Advancing the understanding of allergic contact dermatitis: from pathophysiology to novel therapeutic approaches

Linguistic Validation and Reliability of the Croatian Version of the TOPICOP Questionnaire

Background and Objectives: This study demonstrates the factor structure and reliability of the Croatian version of the TOPICOP (Topical Corticosteroid Phobia) questionnaire, thereby contributing to further validation and standardization of the measurement of topical corticophobia with dermatological patients or their parents, which directly affects patient or parent compliance, as well as the final therapeutic effect. Materials and Methods: The cross-sectional, observational study was conducted at the University Hospital Centre Split, Department of Dermatovenerology. The research involved inviting 120 participants (age 12-68) who attended the University Hospital Centre Split's Atopy School, patients examined in the Dermatology Outpatient Clinic of the University Hospital Centre Split and diagnosed with atopic dermatitis (AD) or allergic contact dermatitis (ACD), and parents or legal representatives of patients younger than 12 years old. The TOPICOP questionnaire consists of 12 items assessing the three different components of topical corticophobia (worries, beliefs, and behaviour). Respondents evaluated their perception of the correctness of each statement within 10 min of filling out the questionnaire on a four-point Likert scale. Results: The response rate was 94%, resulting in a sample of 113 respondents (109 adults and 4 children). Factor analysis yielded one common factor of relatively high reliability (Cronbach α = 0.85, 95% CI 0.81 to 0.89). No differences were found in questionnaire scores between male and female participants, nor between the parents/legal representatives of dermatological patients and other patients. Conclusions: This research contributes to further development of the appropriate measuring instrument, its practical application, and thus, the better recognition, resolution, and prevention of topical corticophobia as part of the better overall healthcare and treatment of chronic dermatological patients.

Rodent models of dermatological disorders

To assess the possible beneficial effects of drugs and drug candidates, different dermatological disease models are available in rodents. These models are able to mimic one or more characteristic features of the disorders, but not completely recapitulate the pathogenesis of the human skin diseases. Therefore, to improve the technology many new models have been developed both by genetic engineering and by chemical or physical induction. Currently the in vivo rodent models provide the physiologically most relevant approach to produce the pathology related to the majority of dermatological diseases. In this short review some widely used animal techniques (psoriasis, allergic contact dermatitis, atopic dermatitis, wound healing, melanoma and non-melanoma type skin cancers and UV erythema) are shown which are currently applied in pharmacological, pharmacokinetic, pharmaceutical and dermatological research. First the main points of the human pathomechanism are shown and afterwards the rodent models are briefly discussed. Finally critical evaluation is provided by the authors. However, according to the 3R rule the number of experimental animals is strongly suggested to be reduced, therefore the advanced in vitro and ex vivo techniques become more and more important contrary to in vivo preclinical methods also in dermatological research. As it is described in the outlook section, although the 2D/3D in vitro and skin on-a-chip techniques are promising and have many advantages they are not able to completely substitute the animal models in their vascular, immunological, secretory and neural complexity.

Contact allergy to SIDAPA baseline series allergens in patients with eyelid dermatitis: An Italian multicentre study

BACKGROUND

Eyelid dermatitis is a frequent reason of dermatological consultation. Its aetiology is not univocal, being contact dermatitis, both allergic and irritant, the most frequent. The primary sources of allergen exposure include cosmetics, metals, and topical medications, from direct, indirect, or airborne contact.

OBJECTIVES

To define the frequency of positive patch test reactions to SIDAPA baseline series allergens, to document positive allergens, and to precise the final diagnosis in patients with eyelid involvement.

METHODS

A total of 8557 consecutive patients from 12 Italian Dermatology Clinics underwent patch testing with SIDAPA baseline series in 2018 and 2019. Patients were divided into two groups: (i) with eyelid involvement with or without other involved sites (E-Group) and (ii) without eyelid involvement (NE-Group). The final diagnosis and the frequency of positive relevant patch test reactions were evaluated.

RESULTS

E-Group consisted of 688 patients (females 78.6%, mean age 45.3 years), 8.0% of 8557 consecutively patch-tested patients. The final diagnosis in E-Group was ADC in 42.4%, ICD in 34.2%, and AD in 30.5%. The highest reaction rates were elicited by nickel sulphate and methylchloroisothiazolinone/methylisothiazolinone in both E-Group and NE-Group, even if these allergens were significantly more frequently positive in NE-Group patients than in E-Group ones. Positive patch test reactions to fragrance Mix II, dimethylaminopropylamine, and sorbitan sesquiolate were significantly more frequent in E-Group patients than in NE-Group ones.

CONCLUSIONS

Eyelid dermatitis is a frequent dermatological complaint. Allergic contact dermatitis is the most frequent diagnosis commonly caused by nickel sulphate, isothiazolinones, and fragrances. The surfactants dimethylaminopropylamine and sorbitan sesquioleate are emerging causes of eyelid allergic contact dermatitis.

The new Italian SIDAPA Baseline Series for patch testing (2023): an update according to the new regulatory pathway for contact allergens

Allergic contact dermatitis (ACD) is a common inflammatory skin disease caused by delayed hypersensitivity to chemical and biotic contact allergens. ACD significantly affects the patients' quality of life negatively impacting both occupational and non-occupational settings. Patch testing is the gold standard diagnostic in vivo test to precise the ACD etiology and to correctly perform prevention. According to the Italian Medicines Agency (AIFA) legislative decree no. 178 of 29th May 1991, allergens are defined as medicines and therefore they are subject to strict regulation. In 2017, AIFA (decree no. 2130/2017) started a procedure to regulate contact allergens on the Italian market and actually the contact allergens temporarily authorized are reported in AIFA decree no. 98/2022, valid until November 2023. The availability on the market of contact allergens to diagnose ACD and continuous updating on the basis of new epidemiological trends are mandatory, jointly with the continuous update of the baseline and integrative series for patch testing. For this reason, the scientific community represented in Italy by the Skin Allergies Study Group of SIDeMaST (Italian Society of Dermatology and Venereology) and SIDAPA (Italian Society of Allergological, Occupational and Environmental Dermatology) are constantly working, in close relationship with the European scientific communities with large expertise in this important sector of the modern Dermatology. Herein, we report the setting up of regulatory legislation by AIFA and the new Italian Adult Baseline Series for patch testing.

Use of guinea pig data to obtain starting points for skin sensitisation risk assessment - A commentary

The increasing drive to understand the likelihood of skin sensitisation from plant protection products (PPPs) in workers and the general public has resulted in recent initiatives to establish a quantitative risk assessment (QRA) methodology applicable to these products and their exposure scenarios. The effective evaluation of skin sensitising substances requires not only the identification of that toxicological hazard, but also determination of relative sensitising potency. Typically, this has been achieved by interpretation of local lymph node assay (LLNA) dose response data, delivering what is known as the EC3 value. This permitted regulatory division of skin sensitisers into defined potency sub-categories, but more importantly enabled derivation of a no expected sensitisation induction level (NESIL) as the point of departure for QRA. However, for many existing substances there is no LLNA data, only older guinea pig results exist. To avoid additional (in vivo) testing, an approach has been outlined to employ guinea pig data and existing regulatory guidelines on the determination of potency sub-categorisation to provide a guinea pig based NESIL. The approach adopts a conservative extrapolation from LLNA NESIL benchmarks to deliver points of departure as the basis for the type of QRA process already in successful use by other industries.

Dendritic cells under allergic condition enhance the activation of pruritogen-responsive neurons via inducing itch receptors in a co-culture study

BACKGROUND

Itch sensitization has been reported in patients with chronic allergic skin diseases and observed in a mouse model of allergic contact dermatitis (ACD). There is evidence suggesting that neuroimmune interactions may contribute to itch sensitization, as an increase in dendritic cells (DCs) within ganglia has been observed during allergic conditions. However, how DCs interact with sensory neurons in ganglia during allergic conditions is still not known. This study aims to investigate the role of DCs in dorsal root ganglion (DRG) under ACD conditions, specifically focusing on itch sensitization within the DRG. The tolylene-2,4-diisocyanate (TDI) mouse model for ACD and the co-culture model of DCs and DRG neurons was employed in this study.

RESULTS

We successfully induced ACD by TDI, as evidenced by the development of edema, elevated total serum IgE levels, and an observed itch reaction in TDI-sensitized mice. Calcium imaging and RT-qPCR analysis revealed that TDI-sensitized mice exhibited signs of peripheral sensitization, including a higher percentage of neurons responding to pruritogens and increased activation and expression of itch receptors in excised DRG of TDI-sensitized mice. Immunofluorescence and flow cytometric analysis displayed an increase of MHCII+ cells, which serves as a marker for DCs, within DRG during ACD. The co-culture study revealed that when DRG neurons were cultured with DCs, there was an increase in the number of neurons responsive to pruritogens and activation of itch receptors such as TRPA1, TRPV1, H1R, and TRPV4. In addition, the immunofluorescence and RT-qPCR study confirmed an upregulation of TRPV4.

CONCLUSIONS

Our findings indicate that there is an increase of MHCII+ cells and itch peripheral sensitization in DRG under TDI-induced ACD condition. It has been found that MHCII+ cells in DRG might contribute to the itch peripheral sensitization by activating itch receptors, as shown through co-culture studies between DRG neurons and DCs. Further studies are required to identify the specific mediator(s) responsible for peripheral sensitization induced by activated DCs.

Anti-Inflammatory and Antipruritic Effects of Remote Ischaemic Postconditioning in a Mouse Model of Experimental Allergic Contact Dermatitis

Background and Objectives: Allergic contact dermatitis is a common type IV hypersensitivity reaction characterised by redness, itching, oedema and thickening of the skin. It occurs in about 7% of the population and its incidence is increasing. It has been observed that the preconditioning of tissues by exposing them to transient ischemia increases resistance to subsequent permanent ischemia, and this phenomenon is called ischemic preconditioning. It has been shown that conditioning in one organ can also protect other organs. The protective effect of remote ischemic preconditioning is thought to be based on the induction of anti-inflammatory responses. The aim of this project was to investigate the anti-inflammatory and antipruritic effects of remote ischemic postconditioning in a mouse model of experimental allergic contact dermatitis. Methods: Experimental allergic contact dermatitis was induced with 1-fluoro-2,4-dinitrobenzene. Remote ischemic postconditioning was performed at 3 and 25 h after the challenge. Ear thickness and number of scratches 24 and 48 h after challenge, as well as cytokine levels and the infiltration of mast cells, neutrophils, CD4+ and CD8+ T lymphocytes in serum and ear tissue at 48 h were measured to determine the effect of RIPsC. Results: Remote ischemic postconditioning decreased ear thickness, one of the symptoms of allergic contact dermatitis (p < 0.0001). It had no significant effect on the number of scratches. It reduced serum IL-17 levels (p < 0.01). It alleviated local inflammation by suppressing CD8+ T lymphocyte and neutrophil infiltration. Conclusions: It was concluded that remote ischemic postconditioning may alleviate the symptoms of allergic contact dermatitis by suppressing CD8+ T lymphocyte and neutrophil infiltration and reducing IL-17 secretion.

Looking beyond Self-Protection: The Eyes Instruct Systemic Immune Tolerance Early in Life

The eyes provide themselves with immune tolerance. Frequent skin inflammatory diseases in young blind people suggest, nonetheless, that the eyes instruct a systemic immune tolerance that benefits the whole body. We tested this premise by using delayed skin contact hypersensitivity (DSCH) as a tool to compare the inflammatory response developed by sighted (S) and birth-enucleated (BE) mice against oxazolone or dinitrofluorobenzene at the ages of 10, 30 and 60 days of life. Adult mice enucleated (AE) at 60 days of age were also assessed when they reached 120 days of life. BE mice displayed exacerbated DSCH at 60 but not at 10 or 30 days of age. AE mice, in contrast, show no exacerbated DSCH. Skin inflammation in 60-day-old BE mice was hapten exclusive and supported by distinct CD8+ lymphocytes. The number of intraepidermal T lymphocytes and migrating Langerhans cells was, however, similar between S and BE mice by the age of 60 days. Our observations support the idea that the eyes instruct systemic immune tolerance that benefits organs outside the eyes from an early age. The higher prevalence of inflammatory skin disorders reported in young people might then reflect reduced immune tolerance associated with the impaired functional morphology of the eyes.

S. epidermidis Rescues Allergic Contact Dermatitis in Sphingosine 1-Phosphate Receptor 2-Deficient Skin

Recent studies have identified a subtype of the S1P-receptor family called sphingosine-1-phosphate receptor 2 (S1PR2), which plays a crucial role in maintaining the skin barrier. It has been observed that S1PR2 and Staphylococcus epidermidis (S. epidermidis) work together to regulate the skin barrier. However, the interaction between these two factors is still unclear. To investigate this, a study was conducted on healthy skin and allergic contact dermatitis (ACD) using 3,4-Dibutoxy-3-cyclobutene-1,2-dione (SADBE) on the ears of S1pr2fl/fl and S1pr2fl/flK14-Cre mice and using 1 × 106 CFU of S. epidermidis to examine its effects on the skin. The results showed that in S. epidermidis-conditioned ACD, the ear thickness of S1pr2fl/flK14-Cre mice was lower than that of S1pr2fl/fl mice, and mRNA expressions of Il-1β and Cxcl2 of S1pr2fl/flK14-Cre mice were lower than that of S1pr2fl/fl mice in ACD with S. epidermidis. Furthermore, the gene expression of Claudin-1 and Occludin in S1pr2fl/flK14-Cre mice was higher than that of S1pr2fl/fl mice in ACD with S. epidermidis. The study concludes that S. epidermidis colonization improves the skin barrier and prevents ACD even when S1P signaling malfunctions.