Allergic contact dermatitis: epidemiology, molecular mechanisms, in vitro methods and regulatory aspects. Current knowledge assembled at an international workshop at BfR, Germany

Contact allergen (PPD and DNCB)-induced keratinocyte sensitization is partly mediated through a low molecular weight hyaluronan (LMWHA)/TLR4/NF-κB signaling axis

Allergic contact dermatitis (ACD) is caused by topical exposure to chemical allergens. Keratinocytes play a key role in innate immunity, as well as in ACD progression. The transmembrane Toll-like receptor 4 (TLR4), strongly implicated in skin inflammation, has the ability to bind Damage Associated Molecular Patterns (DAMPs), like Low Molecular Weight Hyaluronan (LMWHA). Previously, we had determined that p-phenylenediamine (PPD) and 2,4-dinitrochlorobenzene (DNCB) modulate keratinocyte HA deposition in a manner correlated to their sensitization. In the present study, we aimed to investigate putative co-operation of HA and TLR4 in the process of PPD and DNCB-induced keratinocyte activation. Contact sensitizers were shown to significantly increase the expression of Hyaluronan Synthases (HAS) and TLR4 in NCTC2544 human keratinocytes, as demonstrated by western blot and Real-Time PCR. These data, in correlation to earlier shown enhanced HA degradation suggest that the contact sensitizers facilitate HA turnover of keratinocytes and increase the release of pro-inflammatory, LMWHA fragments. Treatment with exogenous LMWHA enhanced TLR4, HAS levels and Nuclear factor-kappa beta (NF-κΒ) activation. PPD, DNCB and LMWHA-effects were shown to be partly executed through TLR4 downstream signaling as shown by Real-Time, western blot, siRNA and confocal microscopy approaches. Specifically, PPD and DNCB stimulated the activation of the TLR4 downstream mediator NF-κB. Therefore, the shown upregulation of TLR4 expression is suggested to further facilitate the release of endogenous, bioactive HA fragments and sustain keratinocyte activation. In conclusion, keratinocyte contact allergen-dependent sensitization is partly mediated through a LMWHA/TLR4/ NF-κB signaling axis.

Prediction of the skin sensitising potential and potency of compounds via mechanism-based binary and ternary classification models

Skin sensitisation, one of the most frequent forms of human immune toxicity, is authenticated to be a significant endpoint in the field of drug discovery and cosmetics. Due to the drawbacks of traditional animal testing methods, in silico methods have advanced to study skin sensitisation. In this study, mechanism-based binary and ternary classification models were constructed with a comprehensive data set. 1007 compounds were collected to develop five series of local and global models based on mechanisms. In each series, compounds were classified into five groups according to EC3 values, and applied as training sets, test sets and external validation sets. For each of the five series, 81 binary classification models and 81 ternary classification models were acquired via 9 molecular fingerprints and 9 machine learning methods using a novel KNIME workflow. Meanwhile, the applicability domains for the best 10 models were figured out to certify the rationality of prediction effect. In addition, 8 toxic substructures probably causing skin sensitisation were identified to speculate whether a compound is a skin sensitiser. The mechanism-based prediction models and the toxic substructures can be applied to predict the skin sensitising potential and potency of compounds.

Activation of Mast-Cell-Expressed Mas-Related G-Protein-Coupled Receptors Drives Non-histaminergic Itch

Classical itch studies have focused on immunoglobulin E (IgE)-mediated mast cell activation and histamine release. Recently, members of the Mas-related G-protein-coupled receptor (Mrgpr) family have been identified as mast cell receptors, but their role in itch is unclear. Here, we report that mast cell activation via Mrgprb2 evoked non-histaminergic itch in mice independently of the IgE-Fc epsilon RI (FcεRI)-histamine axis. Compared with IgE-FcεRI stimulation, Mrgprb2 activation of mast cells was distinct in both released substances (histamine, serotonin, and tryptase) and the pattern of activated itch-sensory neurons. Mrgprb2 deficiency decreased itch in multiple preclinical models of allergic contact dermatitis (ACD), a pruritic inflammatory skin disorder, and both mast cell number and PAMP1-20 concentrations (agonist of the human Mrgprb2 homolog, MRGPRX2) were increased in human ACD skin. These findings suggest that this pathway may represent a therapeutic target for treating ACD and mast-cell-associated itch disorders in which antihistamines are ineffective.

Time for a makeover-cosmetics regulation in the United States

INTRODUCTION

Cosmetics and personal care products are ubiquitous. Consumer pressure arising from recent episodes of products found to be unsafe has led to new policy proposals to modernize cosmetics regulation in the United States.

METHODS

We reviewed contemporary cosmetics regulation and collected major past and current policy proposals relating to cosmetics regulation with a focus on public health controversies.

RESULTS

Under a structure originally established in 1938 that places regulation of cosmetics under the Food and Drug Administration (FDA), cosmetics manufacturers in the United States are not required to register their products or forward consumer complaints to the FDA, leading to broad under-reporting of adverse events. The FDA has limited authority to mandate product recalls. The existing FDA database system that collects adverse events related to cosmetics has limited public health utility. Current proposals for new cosmetics regulations seek to establish better systems for data collection and mandatory manufacturer registrations funded by cosmetic manufacturers. Additional policy changes could include a premarket review process for cosmeceuticals (cosmetics that make drug-like claims) and more advanced real-world data safety monitoring tools.

CONCLUSIONS

With continued consumer concern and several recent cosmetic-related public health controversies, the FDA should be given more resources and broader authority to protect consumer safety.

Experience in patch testing: A 6-year retrospective review from a single academic allergy practice

BACKGROUND

Patch testing is the "gold standard" to identify culprit allergen(s) causing allergic contact dermatitis (ACD), but there are limited studies of patch testing from allergy practice settings.

OBJECTIVE

We sought to explore patch test findings in a large academic allergy practice, including patch testing results, history of atopy, location of dermatitis, and referral source. We also wanted to determine whether patch testing using an extended panel, such as the North American screening series, compared with a limited series, such as the Thin-Layer Rapid-Use Epicutaneous (T.R.U.E.) Test, increased the sensitivity.

METHODS

A retrospective chart review was conducted of patients referred for patch testing over a 6-year period.

RESULTS

A total of 585 patients (mean age 48.7 years, 71.6 % female) underwent patch testing over the 6-year period, of which 369 (63%) had a positive test. Of those who tested positive, 202 (55%) reported a history of atopy. The extremities were the most commonly involved site, followed by the head/neck and trunk. The 5 most common positive allergens were nickel sulfate, gold sodium thiosulfate, methylchloroisothiazolinone, thimerosal, and bacitracin. Three hundred fourteen (53.6%) patients were positive to at least 1 allergen on TRUE testing. Extended screening series identified an additional 10.8% of patients with positive tests who were negative to T.R.U.E. test allergens.

CONCLUSION

Patch testing is a valuable diagnostic tool for the practicing allergist and provides early identification of culprit allergens in ACD. Performing an extended screening series such as the North American Contact Dermatitis Group (NACDG) or supplemental panel of allergens increased sensitivity when compared with a limited series.

Assessment of patch test results carried out during ten years in a city in southern Brazil

BACKGROUND

Contact dermatitis affects up to 20% of the population. Patch testing for contact allergy may be needed to confirm the diagnosis.

OBJECTIVES

To describe and discuss the results of patch tests performed in a city in southern Brazil.

METHODS

A cross-sectional analysis was performed on all skin test results over ten years. Variables such as gender, age at the time of testing, and test results were evaluated. Triggering factors, duration of complain, and previous medications used related to the clinical history were retrieved for some patients by reviewing their medical records.

RESULTS

The sample was composed of 539 patch tests, of which 411 (76.2%) were from women. The age of the tested subjects ranged from 5 to 87 years. The prevalence of positive reactions in the patch tests was 391 (72.5%). The most prevalent positive reaction was to nickel sulfate (196; 36.4%), which had statistical significance when associated with female gender (p<0,001).

STUDY LIMITATIONS

Database obtained through secondary sources (the reports of the exams and the medical records), occurring the incomplete registration of some information.

CONCLUSIONS

Data analysis at the local level is important to define preventive policies.

Allergic Contact Dermatitis and Autoeczematization to Proctosedyl® Cream and Proctomyxin® Cream

Proctosedyl® and Proctomyxin® are two commonly prescribed hemorrhoid therapies. Their topical application to the perianal region may be complicated by a local allergic contact dermatitis and subsequent autoeczematization reaction. We present three cases of an autoeczematization (ID) reaction to varying topical allergens found in Proctosedyl®/Proctomyxin®. It is our recommendation that physician and patient education, avoidance of allergens (or cross-reactants), and appropriate choice of topical corticosteroid is important in preventing and avoiding flares.

Surface Treatment with Non-thermal Humid Argon Plasma as a Treatment for Allergic Contact Dermatitis in a Mouse Model

Cold plasma generated at atmospheric pressure has attracted intense interest in biomedical applications, particularly as an antimicrobial treatment. Here we report the therapeutic effect of humidified cold argon plasma on allergic contact dermatitis (ACD) in a mouse model. Treatment was carried out with different gas compositions: argon gas containing small amounts of either N₂, O₂, or H₂O. The best effect was obtained using humid plasma (H₂O addition), where the ACD symptoms decreased after one or two 1-min plasma treatments. Even for severe ACD with ulcers and crust formation, the humid plasma-treated mice recovered faster than the control group. Histopathological analysis by H&E-staining showed enhanced epithelialization with formation of collagen and hair follicles in the affected skin after humid plasma exposure. The therapeutic ability of the humid argon plasma discharge was proposed to be induced by reactive oxygen species (H_xO_y) transported from the discharge zone, which are adhesive and accumulate on the skin surface, penetrating the subcutis to eliminate inflammation. However, in treatments using plasma with addition of oxygen or nitrogen (without water) the active gaseous species are blocked due to poor adhesion to and penetration into the dry ACD skin, with correspondingly poor treatment effects. The enhanced in vivo healing in ACD mice indicate the non-thermal humid plasma could be a potential alternative approach for therapy of ACD and other inflammatory skin diseases.

Optimizing the cutoff for the identification of skin sensitizers by the HaCaSens assay: Introducing an ROC-analysis-based cutoff approach

The worldwide restricted use of animal testing makes it challenging to identify the skin sensitizing potentials of newly manufactured products. The HaCaSens assay has shown promise as an in vitro skin sensitizing assay comparable to existing assays, and is currently under pre-validation. However, there is little agreement on how to assess the results of the assay to discriminate sensitizers from non-sensitizers as the stimulation index (SI) cutoff value was arbitrarily chosen without appropriate statistical methods. Here, we investigated the SI cutoff values in identifying sensitizers to obtain the optimal value. Sensitivities and specificities were calculated for a set of 30 test substances, and plotted in receiver operator characteristics (ROC) curves. The SI cutoff values with the highest sum of sensitivity and specificity according to LLNA data were 2.2, 1.8 and 3.0 for interleukin 1α (IL-1α), interleukin 6 (IL-6), and the combination of the two cytokines respectively. Also, the same statistical analysis of human data demonstrated optimal SI cutoff values 2.0, 2.0 and 3.2 for the same respective parameters. When considering the predictive capacity of each possible SI cutoff value determined by ROC curves, the optimal value for HaCaSens is 3.0 for the combination of IL-1α and IL-6 as it had the highest sensitivity (90.9%), specificity (75.0%) and accuracy (86.7%) based on LLNA data. Thus, we recommend the wide use of the SI cutoff value of 3.0 to ensure consistent endpoints.

Immune-modulation via IgD B-cell receptor suppresses allergic skin inflammation in experimental contact hypersensitivity models despite of a Th2-favoured humoral response

Atopic dermatitis (AD) and allergic contact dermatitis (ACD) are common skin inflammatory conditions. B and T cells are strongly implicated in allergic contact hypersensitivity (CHS) conditions. Activation of IgD B-cell receptor (BCR) by anti-IgD stimulation depletes mature B cells and modulates T-helper cell type 1/2 (Th1/2) responses in vivo. It is not known whether these effects by anti-IgD exacerbates or ameliorates chronic skin inflammations. This study investigated the effects of anti-IgD and B-cell depleting anti-CD20 antibody on skin inflammation in CHS murine models. Chronic CHS were induced by challenges with allergens trimellitic anhydride (TMA) or 2,4 dinitrochlorobenzene (DNCB). Mice were treated with an anti-IgD or anti-CD20 at various time-points following allergen challenges. This study revealed that early therapeutic treatments with anti-IgD at 4 h after allergen challenge significantly reduced skin inflammation in both TMA- and DNCB-induced CHS models (P < 0.05). In contrast, anti-CD20 treatment exacerbated skin inflammation in DNCB-induced CHS despite of an extensive B cell depletion (P < 0.05). Anti-IgD treatment depleted mature CD19⁺IgD⁺ B cells but enhanced allergen-specific IgM and total IgE productions, suggesting a Th2-favoured humoral response. Anti-IgD reduced neutrophilic infiltrations but increases accumulation of mast cells in dermal tissues. The anti-inflammatory effects of anti-IgD were supported by evidence of an increase in the percentage of regulatory B cells and T cells. Collectively, this study demonstrates that immune-modulation by anti-IgD treatment suppresses Th2-mediated allergic skin inflammation in murine models despite a skew toward a Th2-favvoured humoral response and therefore may present a novel treatment for chronic human AD and ACD.

A highly sensitive and selective high pressure liquid chromatography with tandem mass spectrometry (HPLC/MS-MS) method for the direct peptide reactivity assay (DPRA)

While the HPLC/UV (high performance liquid chromatography coupled with ultra-violet spectrometry)-based DPRA (Direct Peptide Reactivity Assay) identifies dermal sensitizers with approximately 80% accuracy, the low selectivity and sensitivity of the HPLC/UV-based DPRA poses challenges to accurately identify the sensitization potential of certain chemicals. In this study, a high performance liquid chromatography coupled with tandem mass spectrometry (HPLC/MS-MS)-based DPRA was developed and validated according to the test guideline (OECD TG 442C). The final results were compared with the results from the traditional HPLC/UV-based guideline DPRA. This HPLC/MS-MS-based DPRA demonstrated similar performance compared to HPLC/UV-based DPRA using known dermal sensitizers and non-sensitizers according to the test guideline (OECD TG 442C). Following the validation, a challenge set of chemicals with either overlapping retention time with peptides, or higher hydrophobicity or chemicals potentially forming non-covalent interactions with peptides were assessed for dermal sensitization potential using both methods and the results were compared to existing in vivo data. The HPLC/MS-MS-based DPRA correctly predicted these chemicals as sensitizers or non-sensitizers; however, the HPLC/UV-based DPRA resulted in false-positive predictions for hydrophobic substances, chemicals with UV peaks overlapping with those of the peptide(s), and compounds that non-covalently interact with the peptides. These findings demonstrate the broader applicability and better sensitivity and selectivity of the LC/MS-MS-based DPRA over the traditional HPLC/UV-based guideline DPRA.

Dermatology ECHO: A case presentation demonstrating benefits of specialty telementoring in primary care

Allergic contact dermatitis (ACD) is a common dermatologic disorder that is estimated to affect 15-20% of the general population. Because of its prevalence, it may be expected that ACD should be easily recognized. However, it can present with many clinical variations that may complicate diagnosis. Although ACD is a treatable condition, patients from rural and underserved areas suffer if timely access to specialty care is limited. Dermatology Extension for Community Healthcare Outcomes (Dermatology ECHO) telemedicine sessions were created to mentor rural primary care providers (PCPs). To illustrate their benefit, we present the case of a 19-year-old female patient who suffered from worsening undiagnosed ACD for over nine months following a laparoscopic appendectomy. During that time, the surgeon and multiple PCPs treated her with antibiotics, antivirals, and Scabicide without improvement in her condition. The de-identified patient case was presented by her PCP during the Dermatology ECHO session. The Dermatology ECHO specialty team mentored and educated the PCP in the diagnosis and treatment of ACD. After making the diagnosis, the patient received new treatment and her condition improved significantly. Dermatology ECHO provides a knowledge-sharing network for participating PCPs that may improve patient outcomes and reduce patient suffering.

Recent advances in understanding and managing contact dermatitis

About 20% of the general population is contact-sensitized to common haptens such as fragrances, preservatives, and metals. Many also develop allergic contact dermatitis (ACD), the clinical manifestation of contact sensitization. ACD represents a common health issue and is also one of the most important occupational diseases. Although this inflammatory skin disease is mediated predominantly by memory T lymphocytes recognizing low-molecular-weight chemicals after skin contact, the innate immune system also plays an important role. Along that line, the presence of irritants may increase the risk of ACD and therefore ACD is often seen in the context of irritant contact dermatitis. In this review article, we discuss recent progress in basic research that has dramatically increased our understanding of the pathomechanisms of ACD and provides a basis for the development of novel diagnostic and therapeutic measures. Current methods for diagnosis as well as treatment options of ACD are also discussed.

Tri-culture system for pro-hapten sensitizer identification and potency classification

Allergic contact dermatitis (ACD) is an inflammatory disease that impacts 15-20% of the general population and accurate screening methods for chemical risk assessment are needed. However, most approaches poorly predict pre- and pro-hapten sensitizers, which require abiotic or metabolic conversion prior to inducing sensitization. We developed a tri-culture system comprised of MUTZ-3-derived Langerhans cells, HaCaT keratinocytes, and primary dermal fibroblasts to mimic the cellular and metabolic environments of skin sensitization. A panel of non-sensitizers and sensitizers was tested and the secretome was evaluated. A support vector machine (SVM) was used to identify the most predictive sensitization signature and classification trees identified statistical thresholds to predict sensitizer potency. The SVM computed 91% tri-culture prediction accuracy using the top 3 ranking biomarkers (IL-8, MIP-1β, and GM-CSF) and improved the detection of pre- and pro-haptens. This in vitro assay combined with in silico data analysis presents a promising approach and offers the possibility of multi-metric analysis for enhanced ACD sensitizer screening.

An evaluation of selected (Q)SARs/expert systems for predicting skin sensitisation potential

Predictive testing to characterise substances for their skin sensitisation potential has historically been based on animal models such as the Local Lymph Node Assay (LLNA) and the Guinea Pig Maximisation Test (GPMT). In recent years, EU regulations, have provided a strong incentive to develop non-animal alternatives, such as expert systems software. Here we selected three different types of expert systems: VEGA (statistical), Derek Nexus (knowledge-based) and TIMES-SS (hybrid), and evaluated their performance using two large sets of animal data: one set of 1249 substances from eChemportal and a second set of 515 substances from NICEATM. A model was considered successful at predicting skin sensitisation potential if it had at least the same balanced accuracy as the LLNA and the GPMT had in predicting the other outcomes, which ranged from 79% to 86%. We found that the highest balanced accuracy of any of the expert systems evaluated was 65% when making global predictions. For substances within the domain of TIMES-SS, however, balanced accuracies for the two datasets were found to be 79% and 82%. In those cases where a chemical was within the TIMES-SS domain, the TIMES-SS skin sensitisation hazard prediction had the same confidence as the result from LLNA or GPMT.

Silkworm dropping extract ameliorate trimellitic anhydride-induced allergic contact dermatitis by regulating Th1/Th2 immune response

Allergic contact dermatitis (ACD) is an inflammatory skin disease caused by hapten-specific immune response. Silkworm droppings are known to exert beneficial effects during the treatment of inflammatory diseases. Here, we studied whether topical treatment and oral administration of silkworm dropping extract (SDE) ameliorate trimellitic anhydride (TMA)-induced ACD. In ACD mice model, SDE treatment significantly suppressed the increase in both ear thickness and serum IgE levels. Furthermore, IL-1β and TNF-α levels were reduced by SDE. In allergic responses, SDE treatment significantly attenuated the production of the Th2-associated cytokine IL-4 in both ear tissue and draining lymph nodes. However, it increased the production of the Th1-mediated cytokine IL-12. Thus, these results showed that SDE attenuated TMA-induced ACD symptoms through regulation of Th1/Th2 immune response. Taken together, we suggest that SDE treatment might be a potential agent in the prevention or therapy of Th2-mediated inflammatory skin diseases such as ACD and atopic dermatitis.

ABBREVIATIONS

ACD: allergic contact dermatitis; AD: atopic dermatitis; APC: antigen presenting cells; CCL: chemokine (C-C motif) ligand; CCR: C-C chemokine receptor; Dex: dexamethasone; ELISA: enzyme-linked immunosorbent assay; IFN: interferon; Ig: immunoglobulin; IL: interleukin; OVA: ovalbumin; PS: prednisolone; SDE: silkworm dropping extract; Th: T helper; TMA: trimellitic anhydride; TNF: tumor necrosis factor.

Lymphocyte surface markers and cytokines are suitable for detection and potency assessment of skin-sensitizing chemicals in an in vitro model of allergic contact dermatitis: the LCSA-ly

Allergic contact dermatitis is a widespread health disorder and occupational skin disease. Hence, screening for contact-sensitizing chemicals is highly relevant to toxicology, dermatology, and occupational medicine. The use of animal tests for this purpose is constrained by ethical considerations, need for high-throughput screening, and legislation (e.g., for cosmetics in the European Union). T cell activation is the final and most specific key event of the "adverse outcome pathway" for skin sensitization and therefore a promising target for the development of in vitro sensitization assays. We present a novel in vitro sensitization assay with a lymphocyte endpoint as an add-on to the loose-fit coculture-based sensitization assay (LCSA): the LCSA-ly. While the LCSA measures dendritic cell activation, the LCSA-ly offers the option for an additional lymphocyte endpoint which can be measured concurrently. We incorporated lymphocytes in our previously established coculture of primary human keratinocytes and monocyte-derived dendritic cells and tested nine substances: five sensitizers [2,4-dinitrochlorobenzene (DNCB) 1.25-15 µmol/l, p-phenylenediamine (PPD) 15.6-125 µmol/l, 2-mercaptobenzothiazole (MBT) 50-1000 µmol/l, coumarin, and resorcinol (both: 250-1500 µmol/l)] and four non-sensitizers (monochlorobenzene, caprylic acid, glycerol, and salicylic acid (all: 125-1000 µmol/l)]. DNCB and MBT increased a subset of IL-23 receptor+/IFN-γ receptor 1 (CD119)+ lymphocytes. DNCB, PPD, and MBT enhanced a subunit of the IL-4 receptor (CD124) and a memory marker (CD44) on lymphocytes. Remarkably, DNCB, PPD, and MBT raised IL-4 concentrations in coculture supernatants while IFN-γ levels decreased, which might point to Th2 activation in vitro. Coumarin, resorcinol, and non-sensitizers did not alter any of the tested surface markers or cytokines. IL-17 was not affected by any of the substances. Relative strength of sensitizers according to lymphocyte markers was DNCB > PPD > MBT, which corresponds to earlier results from the LCSA without lymphocyte endpoint, the murine local lymph node assay, and human data. This study is the first to prove the suitability of lymphocyte surface markers for sensitization testing and potency assessment.

Modulation of CYP1A1 metabolism: From adverse health effects to chemoprevention and therapeutic options

The human cytochrome P450 (CYP) 1A1 gene encodes a monooxygenase that metabolizes multiple exogenous and endogenous substrates. CYP1A1 has become infamous for its oxidative metabolism of benzo[a]pyrene and related polycyclic aromatic hydrocarbons, converting these chemicals into very potent human carcinogens. CYP1A1 expression is mainly controlled by the aryl hydrocarbon receptor (AHR), a transcription factor whose activation is induced by binding of persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins. Accordingly, induction of CYP1A1 expression and activity serves as a biomarker of AHR activation and associated xenobiotic metabolism as well as toxicity in diverse animal species and humans. Determination of CYP1A1 activity is integrated into modern toxicological concepts and testing guidelines, emphasizing the tremendous importance of this enzyme for risk assessment and regulation of chemicals. Further, CYP1A1 serves as a molecular target for chemoprevention of chemical carcinogenesis, although present literature is controversial on whether its inhibition or induction exerts beneficial effects. Regarding therapeutic applications, first anti-cancer prodrugs are available, which require a metabolic activation by CYP1A1, and thus enable a specific elimination of CYP1A1-positive tumors. However, the application range of these drugs may be limited due to the frequently observed downregulation of CYP1A1 in various human cancers, probably leading to a reduced metabolism of endogenous AHR ligands and a sustained activation of AHR and associated tumor-promoting responses. We here summarize the current knowledge on CYP1A1 as a key player in the metabolism of exogenous and endogenous substrates and as a promising target molecule for prevention and treatment of human malignancies.

The Fate of a Hapten - From the Skin to Modification of Macrophage Migration Inhibitory Factor (MIF) in Lymph Nodes

Skin (contact) allergy, the most prevalent form of immunotoxicity in humans, is caused by low molecular weight chemicals (haptens) that penetrate stratum corneum and modify endogenous proteins. The fate of haptens after cutaneous absorption, especially what protein(s) they react with, is largely unknown. In this study the fluorescent hapten tetramethylrhodamine isothiocyanate (TRITC) was used to identify hapten-protein conjugates in the local lymph nodes after topical application, as they play a key role in activation of the adaptive immune system. TRITC interacted with dendritic cells but also with T and B cells in the lymph nodes as shown by flow cytometry. Identification of the most abundant TRITC-modified protein in lymph nodes by tandem mass spectrometry revealed TRITC-modification of the N-terminal proline of macrophage migration inhibitory factor (MIF) – an evolutionary well-conserved protein involved in cell-mediated immunity and inflammation. This is the first time a hapten-modified protein has been identified in lymph nodes after topical administration of the hapten. Most haptens are electrophiles and can therefore modify the N-terminal proline of MIF, which has an unusually reactive amino group under physiological conditions; thus, modification of MIF by haptens may have an immunomodulating role in contact allergy as well as in other immunotoxicity reactions.

A multi-omics analysis reveals metabolic reprogramming in THP-1 cells upon treatment with the contact allergen DNCB

Dendritic cell (DC) activation by contact allergens is one of the key steps in the development of allergic contact dermatitis (ACD). Recent evidence suggests that metabolic reprogramming is a prerequisite for the activation of DCs, macrophages and monocytes. Therefore, we used an integrated approach by combining proteomics and metabolomics to investigate the metabolism of human THP-1 cells in response to the strong contact allergen, 2,4-dinitrochlorobenzene (DNCB). Cells were treated with 5, 10 and 20μM DNCB for 4, 8, and 24h, respectively. Using a targeted metabolomics approach, we quantified levels of 188 endogenous metabolites, among them phospholipids, acylcarnitines, amino acids and hexoses. In addition, proteomic changes were analyzed using an untargeted quantitative approach based on stable isotope labeling with amino acids in cell culture (SILAC). We detected several alterations in the metabolome and consistently in the proteome indicating metabolic reprogramming of THP-1 cells by DNCB. In particular, we found an increase in phospholipids that was accompanied by an up-regulation of fatty acid synthase (FAS), a key enzyme in lipid synthesis.

The 17,18-epoxyeicosatetraenoic acid-G protein-coupled receptor 40 axis ameliorates contact hypersensitivity by inhibiting neutrophil mobility in mice and cynomolgus macaques

BACKGROUND

Metabolites of eicosapentaenoic acid exert various physiologic actions. 17,18-Epoxyeicosatetraenoic acid (17,18-EpETE) is a recently identified new class of antiallergic and anti-inflammatory lipid metabolite of eicosapentaenoic acid, but its effects on skin inflammation and the underlying mechanisms remain to be investigated.

OBJECTIVE

We evaluated the effectiveness of 17,18-EpETE for control of contact hypersensitivity in mice and cynomolgus macaques. We further sought to reveal underlying mechanisms by identifying the responsible receptor and cellular target of 17,18-EpETE.

METHODS

Contact hypersensitivity was induced by topical application of 2,4-dinitrofluorobenzene. Skin inflammation and immune cell populations were analyzed by using flow cytometric, immunohistologic, and quantitative RT-PCR analyses. Neutrophil mobility was examined by means of imaging analysis in vivo and neutrophil culture in vitro. The receptor for 17,18-EpETE was identified by using the TGF-α shedding assay, and the receptor's involvement in the anti-inflammatory effects of 17,18-EpETE was examined by using KO mice and specific inhibitor treatment.

RESULTS

We found that preventive or therapeutic treatment with 17,18-EpETE ameliorated contact hypersensitivity by inhibiting neutrophil mobility in mice and cynomolgus macaques. 17,18-EpETE was recognized by G protein-coupled receptor (GPR) 40 (also known as free fatty acid receptor 1) and inhibited chemoattractant-induced Rac activation and pseudopod formation in neutrophils. Indeed, the antiallergic inflammatory effect of 17,18-EpETE was abolished in the absence or inhibition of GPR40.

CONCLUSION

17,18-EpETE inhibits neutrophil mobility through GPR40 activation, which is a potential therapeutic target to control allergic inflammatory diseases.

Assessing the validity of self-reported history of rash caused by metal or jewellery

BACKGROUND

The use of metal-containing bio-devices is becoming increasingly common. Self-reported history of dermatitis with metal exposure is not established as being predictive for metal allergy.

OBJECTIVES

To assess the validity of two screening questions addressing metal allergy.

METHODS

At Massachusetts General Hospital Contact Dermatitis Clinic, 2132 consecutive patients were asked either 'Do you get rashes when jewellery touches your skin' (Q1; N = 1816) or 'Do you get rashes when metal touches your skin?' (Q2; N = 316) before being patch tested.

RESULTS

Testing showed that 20% of subjects had positive reactions to nickel, 7.4% had positive reactions to cobalt, and 5.8% had positive reactions to chromium. Q1 was 40% sensitive (95%CI: 35-45%). The positive predictive value (PPV) was 51%, and the negative predictive value (NPV) was 82%. Q2 was 77% sensitive (95%CI: 68-84%). The PPV was 71%, and the NPV was 84%. Q2 was 37% more sensitive than Q1 (p < 0.0001), with a higher relative risk (RR) (4.75, p < 0.001) than Q1 (RR = 3.01, p < 0.001).

CONCLUSIONS

Patient-reported metal allergy, although not perfect, is a reasonable method for metal allergy screening to help identify those needing further objective evaluation by patch testing.

Decursin and decursinol angelate: molecular mechanism and therapeutic potential in inflammatory diseases

Epidemiological studies have shown that inflammation plays a critical role in the development and progression of various chronic diseases, including cancers, neurological diseases, hepatic fibrosis, diabetic retinopathy, and vascular diseases. Decursin and decursinol angelate (DA) are pyranocoumarin compounds obtained from the roots of Angelica gigas. Several studies have described the anti-inflammatory effects of decursin and DA. Decursin and DA have shown potential anti-inflammatory activity by modulating growth factors such as vascular endothelial growth factor, transcription factors such as signal transducer and activator of transcription 3 and nuclear factor kappa-light-chain-enhancer of activated B cells, cellular enzymes including matrix metalloproteinases cyclooxygenase, and protein kinases such as extracellular receptor kinase, phosphatidylinositol-3-kinase, and protein kinase C. These compounds have the ability to induce apoptosis by activating pro-apoptotic proteins and the caspase cascade, and reduced the expression of anti-apoptotic proteins such as B-cell lymphoma 2 and B-cell lymphoma-extra-large. Interaction with multiple molecular targets and cytotoxic effects, these two compounds are favorable candidates for treating various chronic inflammatory diseases such as cancers (prostate, breast, leukemia, cervical, and myeloma), rheumatoid arthritis, diabetic retinopathy, hepatic fibrosis, osteoclastogenesis, allergy, and Alzheimer's disease. We have summarized the preliminary studies regarding the biological effects of decursin and DA. In this review, we will also highlight the functions of coumarin compounds that can be translated to a clinical practice for the treatment and prevention of various inflammatory ailments.

Age and Spatial Peculiarities of Non-neoplastic Diseases of the Skin and Subcutaneous Tissue in Kazakhstan, 2003-2015

BACKGROUND

Arrangement of effective management aimed at improving dermatological services and consistent care of patients with skin diseases depends on understanding the epidemiological situation.

METHODS

This retrospective study presents an epidemiological assessment of non-neoplastic skin and subcutaneous tissue diseases in Kazakhstan registered in 2003-2015.

RESULTS

The yearly incidence rate of the diseases among the whole population was in average 3,341.8±121.1 per 100000 population. This represents 4835.0±156.1 for children, 5503.2±141.8 for adolescents and 2646.6±106.7 for adults per 100000 inhabitants. Space and time incidence rate was evaluated according to the administrative division. The overall trend decreased to 3.5% in children to 2.8% in adolescents to 1.9%, and in adults to 3.9%. Considerable variation in rates was seen across the country, with highest rates in East Kazakhstan, Mangystau and Aktobe regions, the lowest - in Atyrau and South-Kazakhstan regions.

CONCLUSION

Non-neoplastic diseases of skin and subcutaneous tissue continue to be an urgent public health problem, especially among children in many regions of Kazakhstan.

Application of proteomics in the elucidation of chemical-mediated allergic contact dermatitis

Allergic contact dermatitis (ACD) is a widespread hypersensitivity reaction of the skin. The cellular mechanisms underlying its development are complex and involve close interaction of different cell types of the immune system. It is this very complexity which has long prevented straightforward replacement of the corresponding regulatory in vivo tests. Recent efforts have already resulted in the development of several in vitro testing alternatives that address key steps of ACD. Yet identification of suitable biomarkers is still a subject of intense research. Search strategies for the latter encompass transcriptomics, proteomics as well as metabolomics approaches. The scope of this review shall be the application and use of proteomics in the context of ACD. This includes highlighting relevant aspects of the molecular and cellular mechanisms underlying ACD, the exploitation of these mechanisms for testing and biomarkers (e.g., in the context of the OECD's adverse outcome pathway initiative) as well as an outlook on emerging proteome targets, for example during the allergen-induced activation of dendritic cells (DCs).

Profile of patients admitted to a triage dermatology clinic at a tertiary hospital in São Paulo, Brazil

Background

Knowledge of epidemiological data on skin diseases is important in planning preventive strategies in healthcare services.

Objective

To assess data from patients admitted to a triage dermatology clinic.

Methods

A retrospective study was performed of patients admitted over a one-year period to the Triage Dermatology Clinic at the Hospital das Clínicas of the University of São Paulo Medical School. Data were obtained from record books. The variables analyzed were: patient age, gender, dermatologic disease (initial diagnosis), origin (from where the patient was referred) and destination (where the patient was referred to).

Results

A total of 16,399 patients and 17,454 diseases were identified for analysis. The most frequent skin disorders were eczema (18%), cutaneous infections (13.1%), erythematous squamous diseases (6.8%) and malignant cutaneous neoplasms (6.1%). Atopic dermatitis was the most common disease in children. Acne was more common among children and adults, as were viral warts. Basal cell carcinoma and squamous cell carcinoma were more common in the elderly. Contact dermatitis and acne predominated in women. The most frequent origins were: the primary/secondary health system (26.6%), other outpatient specialties (25.5%), emergency care (14.9%); while the destinations were: discharged (27.5%), follow-up in our Dermatology Division (24.1%), return (14.1%) and the primary/secondary health system (20.7%).

Conclusion

Understanding the incidence of skin diseases is fundamental in making decisions regarding resource allocation for clinical care and research. Thus, we believe our findings can contribute to improving public health policies.