Lay Abstract

While most patient with PSO or AD have unique skin symptoms/signs that define those conditions, a significant subset of patients (2-20% by some estimates) have features of both diseases, making treatment challenging. Both conditions are influenced by differ-ent types of immune cells and cytokines, which we aim to study in depth using a new (unpublished) model of combined PSO and AD. This project involves creating a mouse model that combines symptoms of psoriasis and atopic dermatitis, two common skin conditions. By studying how these conditions interact, we hope to find new ways to treat patients who suffer from both diseases. Our goal is to understand the underlying immune responses and explore potential treatments that could improve symptoms for these patients.

INTRODUCTION

Psoriasis is among the most common autoimmune diseases with a prevalence of ~2-3% of the US population. It is triggered by T-cells that produce IL-17A/F, which in turn activates growth and differentiation of epidermal keratinocytes. Plaque psoriasis ap-pears as erythematous, silvery white patches of skin. Atopic dermatitis (AD) is driven by Th2 cells that over-produce IL-4 and IL-13, which activate keratinocytes along with in-nate immune cells including mast cells, basophils, eosinophils, and macrophages [1]. AD can present with features that overlap with psoriasis [2], raising the question of whether these are truly two different diseases or one spectrum [3] in light of the fact that a significant fraction of PSO patients (2-20%) have concomitant AD [2]. Interest-ingly, Asian patients with AD not only exhibit psoriasis-like hyperplasia and parakerato-sis but also show activation of the Th17 pathway [4]. Moreover, patients with AD can develop psoriatic lesions following treatment with dupilumab [5] and patients treated for psoriasis with biologics have often been reported to developed AD-like symptoms, a phenomenon called “paradoxical” [9, 10]. Some of these PSO-AD patients experienced symptom relief after undergoing treatment with anti-IL-4/IL-13 combined with anti-IL-17/IL-23 therapy for both diseases. Advancements in diagnosis of psoriasis and AD highlight the possibility that they should not be classified as distinct diseases in that they share genotypic and phenotypic components. Treatment of patients with both AD/PSO can be challenging and require use of multiple biologics [6].

HYPOTHESIS

We hypothesize that one or more cytokines that are unique to this model of AD-PSO are essential to the development of the combined phenotype. In light of that hypothesis, we propose that inhibition of these “driver” cytokines, which are not necessarily IL-17A/F or IL-4/13, can ameliorate disease in the AD-PSO murine model and offer potential for investigation in humans with concomitant AD-PSO-like features.

METHODS

Per references [8] for the MC903 model and [12] for the IL-23MC model, single-treated mice will be treated on day with 10-20ng of IL23MC per hydrodynamic delivery in a volume of saline equal to 10% of the body weight of the mice or every day starting on day 1 with 1.125 nM of MC903 in vehicle on both sides of the ear daily for 10-15 days. For dual treatment, both IL-23MC and MC903 will be initiated started on day one using the protocols mentioned.

We will employ Qiagen RT2 Profiler arrays (Th17: PAMM-073Z; Th1/2: PAMM-034Z; neutrophil/inflammation: LAMM-047Z) on ear skin from IL-23MC-, MC903-, and dual-treated mice to map cytokine profiles, leveraging our published RNA isolation methods. Neutrophil-rich dual-treatment samples (Fig. 1F) will undergo pathway analysis to identify unique inflammatory signatures. For protein-level validation, we will apply our established flow cytometry protocols to quantify intracellular IL-17A/IL-4 and surface markers in ear/lymph node cells, addressing discrepancies between mRNA and protein expression observed in prior work.

Fig. 1. A new murine model for understanding combined features of psoriasis and atopic dermatitis using a single systemic injection of 10-20ug of IL-23 minicircle DNA and published dosing and application of topical MC903 over the course of 10-15 days.

Results

We created a mouse model of AD-PSO by simultaneously administrating a single sys-temic IL-23MC iv injection (10-20ng DNA per injection) and topical MC903 (1.125nm per side of ear, daily x 10-15 days) according to established protocols published by us [7] and others [8] [11] (Fig. 1 and 2). Strikingly, the combined use of systemic IL-23 and topical MC903 resulted in an enhanced clinical skin phenotype at earlier times and with increased skin scaling, erythema, and thickening clinically and histologically (Fig. 2A, B). Preliminary analysis suggested that both IL-4 mRNA and IL-17 cytokine mRNAs are expressed in the skin of mice treated with the combined agents (Fig. 2D).
Observations and measurements of ear lesions were conducted on days 5, 10, and 15 (Fig. 2). Histological analysis confirmed the significant increase in epidermal thickness and a marked increase in the number of. Munro microabscesses in the co-treatment group compared to either IL-23MC or MC903 treatment alone (Fig. 2B, C).
Co-treatment with IL-23MC and MC903 in a psoriasis-AD mouse model revealed mixed Th2/Th17 inflammation. TNF-α and IFN-γ decreased, while IL-10 and IL-4 increased, though IL-4 did not suppress IL-17A/F-contrary to prior reports. IL-17A/F and IL-22 levels remained elevated compared to controls but reduced versus IL-23MC alone, while IL-36G was upregulated. Th2 markers (IL-4, IL-13, TSLP, Foxp3) and IL-33 rose, but IL-5/IL-25 declined. Inflammatory mediators (IL-1β, IL-6, CXCL1/2, CCL20) surged, and neutrophils increased significantly.

Fig. 2. Co-treatment with IL-23MC and MC903 results in an earlier onset of skin lesions and more severe symptoms in the combined disease mouse model. (a) Ear lesions in mice show that on days 10 post-modeling with IL-23MC and MC903 treat-ment; (b) H&E staining of ear skin of controls, IL-23MC, MC903, and combined treatment mice. Scale bar = 100 μm; (c) Munro microabscesses in the ear lesions of mice was quan-tified by counting the microabscesses on the HE-stained sections; (d) On day 10, RT-PCR was performed to assess the gene expression.

Flow cytometry showed elevated IL-4+ T cells, γδ T cells, and neutrophils in lesions and lymph nodes, but fewer IL-17A+ CCR6+ cells in ears. Histologically, co-treatment exacerbated disease severity, with Th17 cytokines (IL-17A/F) rising ~5000-fold versus milder Th2-associated IL-36G (~1-3-fold). IL-23MC dosing (2–10 µg) intensified lesions and cytokine expression (TNF-α, IL-1β, S100A8/A9), peaking at 10 µg. Delayed IL-23MC administration (day 5 vs. day 1) amplified IL-10, IFN-γ, and Th2/Th17 cytokines, confirming 6 µg as optimal for phenotype induction.

Fig. 2. Flow cytometry of ear skin from single and dual-treated mice. (e, f) By flow cytometry, IL-4+ T cells, γδ T cells, IL-17+CCR6+ T cells, Treg and neutrophils were enumerated from (e) ear lesions and (f) lymph nodes that were collected from mice.

Fig. 3. Effect of dosing on severity of dermatitis and expression of cytokines in the skin in the IL-23MC-MC903 murine model.

CONCLUSIONS

Our combined murine model using systemic IL-23 and topical MC903 successfully induces skin inflammation with features of both psoriasis and atopic dermatitis, including simultaneous upregulation of Th2 and Th17 cytokines. This model demonstrates more severe and rapid disease than either treatment alone, and allows investigation of the immune mechanisms underlying overlapping disease phenotypes. It provides a useful platform to identify key cytokines driving the combined pathology and to test targeted therapies that may benefit patients with both psoriasis and atopic dermatitis.

REFERENCES

1. Guttman-Yassky, E. and J.G. Krueger, Atopic dermatitis and psoriasis: two different immune diseases or one spectrum? Curr Opin Immunol, 2017. 48: p. 68-73.
2. Kouwenhoven, T.A., et al., Psoriasis dermatitis: an overlap condition of psoriasis and atopic dermatitis in children. J Eur Acad Dermatol Venereol, 2019. 33(2): p. e74-e76.
3. Bozek, A., M. Zajac, and M. Krupka, Atopic Dermatitis and Psoriasis as Overlapping Syndromes. Mediators Inflamm, 2020. 2020: p. 7527859.
4. Noda, S., et al., The Asian atopic dermatitis phenotype combines features of atopic dermatitis and psoriasis with increased TH17 polarization. J Allergy Clin Immunol, 2015. 136(5): p. 1254-64.
5. Gerger, V., et al., Safety and efficacy of blocking IL-4/13 and IL-23 in concomitant atopic dermatitis and psoriasis - two case reports. J Dtsch Dermatol Ges, 2023. 21(6): p. 648-650.
6. Barry, K., et al., Concomitant atopic dermatitis and psoriasis - a retrospective review. J Dermatolog Treat, 2021. 32(7): p. 716-720.
7. Shi, Z., et al., Differential Requirement for CCR6 in IL-23-Mediated Skin and Joint Inflammation. J Invest Dermatol, 2020.
8. Moosbrugger-Martinz, V., M. Schmuth, and S. Dubrac, A Mouse Model for Atopic Dermatitis Using Topical Application of Vitamin D3 or of Its Analog MC903. Methods Mol Biol, 2017. 1559: p. 91-106.
9. Mendes Roncada, E.V., et al., Atopic Dermatitis as a Paradoxical Effect of Secukinumab for the Treatment of Psoriasis. Case Rep Dermatol, 2021. 13(2): p. 336-339.
10. Zhang, Y. and G. Jiang, Application of JAK inhibitors in paradoxical reaction through immune-related dermatoses. Front Immunol, 2024. 15: p. 1341632.
11. Tamari, M., et al., Difelikefalin suppresses itch and reduces scratching independent of inflammation in a murine model of atopic dermatitis. J Allergy Clin Immunol, 2023. 152(4): p. 927-932.
12. Shi, Z., et al., Targeting the CCR6/CCL20 axis in entheseal and cutaneous inflammation. Arthritis Rheumatol, 2021. 73: p. 2271-83.

ACKNOWLEDGEMENTS

We have no conflicts of interest in this study.