The Pathology of Type 2 Inflammation-Associated Itch in Atopic Dermatitis

Efficacy and safety of dupilumab with concomitant topical corticosteroids in Japanese pediatric patients with moderate-to-severe atopic dermatitis: A randomized, double-blind, placebo-controlled phase 3 study

BACKGROUND

We investigated the efficacy and safety of dupilumab in Japanese patients aged ≥6 months to <18 years old with moderate-to-severe atopic dermatitis not adequately controlled with existing therapies.

METHODS

In this randomized, double-blind, phase 3 study, patients received dupilumab (n = 30) or placebo (n = 32) with concomitant topical corticosteroids for 16 weeks, then all patients received dupilumab from 16 to 52 weeks. The primary endpoint was the proportion of patients with ≥75% improvement in Eczema Area and Severity Index (EASI) score from baseline (EASI-75) to Week 16. Key secondary endpoints included changes in EASI score, proportion of patients with investigator global assessment (IGA) scores of 0/1, and changes in worst daily itch numerical rating scale (NRS) scores (evaluated in patients aged ≥6 to <12 years [n = 35]).

RESULTS

At Week 16, more patients achieved EASI-75 with dupilumab than placebo (43.3% vs 18.8%; P = 0.0304), and the least squares mean (LSM) difference in percent change in EASI scores at Week 16 of dupilumab vs placebo was -39.4% (P = 0.0003). However, no significant difference in the proportion of patients achieving IGA scores of 0/1 at Week 16 with dupilumab versus placebo were seen (10.0% vs 9.4%; P = 0.8476). The percent change in worst daily itch NRS scores at Week 16 was higher with dupilumab (LSM difference: -33.3%; nominal P = 0.0117). Dupilumab was well tolerated; no new safety signals were identified.

CONCLUSIONS

Dupilumab showed consistent efficacy and was well tolerated in Japanese patients aged ≥6 months to <18 years with moderate-to-severe atopic dermatitis previously insufficiently controlled with existing therapies.

Update on the pathogenesis of atopic dermatitis

Atopic dermatitis is a chronic, recurrent, and multifactorial skin-mucosal manifestation resulting from the interaction between elements mainly associated with the skin barrier deficit, the homeostasis of the immune response, neurological aspects, and patterns of reactivity to environmental antigens, which are established in genetically predisposed individuals. In addition to the skin, atopic diathesis involves other organs such as the airways (upper and lower), eyes, digestive tract, and neuropsychiatric aspects, which inflict additional morbidity on the dermatological patient. The different phenotypes of the disease fundamentally depend on the participation of each of these factors, in different life circumstances, such as age groups, occupational exposure patterns, physical activity, pollution, genetic load, and climatic factors. A better understanding of the complexity of its pathogenesis allows not only the understanding of therapeutic targets but also how to identify preponderant elements that mediate disease activity in each circumstance, for selecting the best treatment strategies and mitigation of triggering factors. This narrative review presents an update on the pathogenesis of atopic dermatitis, especially aimed at understanding the clinical manifestations, the main disease phenotypes and the context of available therapeutic strategies.

Interplay between diabetes mellitus and atopic dermatitis

Inflammatory dermatoses such as atopic dermatitis (AD) have long been linked to the pathogenesis of diabetes mellitus. Indeed, numerous studies show an increased risk of diabetes mellitus in individuals with AD although lower prevalence of diabetes mellitus is also observed in few studies. Though the underlying mechanisms accounting for the reciprocal influence between these two conditions are still unclear, the complex interplay between diabetes mellitus and AD is attributable, in part, to genetic and environmental factors, cytokines, epidermal dysfunction, as well as drugs used for the treatment of AD. Proper management of one condition can mitigate the other condition. In this review, we summarize the evidence of the interaction between diabetes mellitus and AD, and discuss the possible underlying mechanisms by which these two conditions influence each other.

Propionate alleviates itch in murine models of atopic dermatitis by modulating sensory TRP channels of dorsal root ganglion

BACKGROUND

Itch is the most common symptom of atopic dermatitis (AD) and significantly decreases the quality of life. Skin microbiome is involved in AD pathogenesis, whereas its role in the regulation of itch remains elusive. In this study, we aimed to investigate the effects of skin microbial metabolite propionate on acute and chronic pruritus and to explore the mechanism.

METHODS

Using various mouse models of itch, the roles of propionate were explored by behavioral tests and histopathology/immunofluorescent analysis. Primary-cultured dorsal root ganglion neurons and HEK293 cells expressing recombinant human TRP channels were utilized for in vitro calcium imaging/in vivo miniature two-photon imaging in combination with electrophysiology and molecular docking approaches for investigation of the mechanism.

RESULTS

Propionate significantly alleviated itch and alloknesis in various mouse models of pruritus and AD and decreased the density of intraepidermal nerve fibers. Propionate reduced the responsiveness of dorsal root ganglion neurons to pruritogens in vitro, attenuated the hyper-excitability in sensory neurons in MC903-induced AD model, and inhibited capsaicin-evoked hTRPV1 currents (IC50 = 20.08 ± 1.11 μM) via interacting with the vanilloid binding site. Propionate also decreased the secretion of calcitonin gene-related peptide by nerves in MC903-induced AD mouse model, which further attenuated itch and skin inflammation.

CONCLUSION

Our study revealed a protective effect of propionate against persistent itch through direct modulation of sensory TRP channels and neuropeptide production in neurons. Regulation of itch via the skin microbiome might be a novel strategy for the treatment of AD.

Efficacy and Safety of PF-07038124 in Patients With Atopic Dermatitis and Plaque Psoriasis: A Randomized Clinical Trial

Importance

Atopic dermatitis (AD) and plaque psoriasis are inflammatory skin diseases with unmet need for effective topical treatments with few application site reactions.

Objective

To assess the efficacy and safety of the topical phosphodiesterase 4 inhibitor PF-07038124 in patients with AD and plaque psoriasis.

Design, Setting, and Participants

This phase 2a, randomized, double-blind clinical trial was conducted from December 21, 2020, to August 18, 2021, at 34 sites across 4 countries. Eligible patients (aged 18-70 years) had mild to moderate AD (covering 5%-20% body surface area) or plaque psoriasis (covering 5%-15% body surface area). Data were analyzed until December 15, 2021.

Interventions

Patients were randomized (1:1) to PF-07038124, 0.01%, topical ointment or vehicle once daily for 6 weeks.

Main Outcomes and Measures

The primary end point was the percent change from baseline (CFB) in the Eczema Area and Severity Index (EASI) total score among patients with AD and in the Psoriasis Area and Severity Index (PASI) score among patients with plaque psoriasis at week 6. Safety measures included treatment-emergent adverse events, including application site reactions.

Results

Overall, 104 patients were randomized (mean [SD] age, 43.0 [15.4] years; 55 [52.9%] women; 4 [3.8%] Asian, 13 [12.5%] Black, and 87 [83.7%] White), including 70 with AD (41 women [58.6%]; mean [SD] ages, 41.4 [16.6] years in the PF-07038124 group and 36.1 [13.9] years in the vehicle group) and 34 with plaque psoriasis (20 men [58.8%]; mean [SD] ages, 51.8 [12.3] years in the PF-07038124 group and 51.2 [10.8] years in the vehicle group). Baseline characteristics were generally balanced. At week 6, the PF-07038124 groups showed significantly greater improvements compared with vehicle groups in EASI (least-squares mean CFB, -74.9% vs -35.5%; difference, -39.4% [90% CI, -58.8% to -20.1%]; P < .001) and PASI scores (CFB, -4.8 vs 0.1; difference, -4.9 [90% CI, -7.0 to -2.8]; P < .001). The number of patients with treatment-emergent adverse events was comparable between treatment groups in patients with AD (PF-07038124, 9 [25.0%]; vehicle, 9 [26.5%]) and plaque psoriasis (PF-07038124, 3 [17.6%]; vehicle, 6 [35.3%]). There were no application site reactions with PF-07038124 treatment.

Conclusions and Relevance

Topical PF-07038124 was well tolerated and demonstrated superior efficacy compared with vehicle in patients with mild to moderate AD and plaque psoriasis.

Trial Registration

ClinicalTrials.gov Identifier: NCT04664153.

Parnassin, a Novel Therapeutic Peptide, Alleviates Skin Lesions in a DNCB-Induced Atopic Dermatitis Mouse Model

Atopic dermatitis (AD) is a chronic inflammatory skin disease which requires continuous treatment due to its relapsing nature. The current treatment includes steroids and nonsteroidal agents targeting inflammation but long-term administration causes various side effects such as skin atrophy, hirsutism, hypertension and diarrhea. Thus, there is an unmet need for safer and effective therapeutic agents in the treatment of AD. Peptides are small biomolecule drugs which are highly potent and remarkably have less side effects. Parnassin is a tetrapeptide with predicted anti-microbial activity curated from Parnassius bremeri transcriptome data. In this study, we confirmed the effect of parnassin on AD using a DNCB-induced AD mouse model and TNF-α/IFN-γ-stimulated HaCaT cells. In the AD mouse model, topical administration of parnassin improved skin lesions and symptoms in AD mice, such as epidermal thickening and mast cell infiltration, similar to the existing treatment, dexamethasone, and did not affect body weight, or the size and weight of spleen. In TNF-α/IFN-γ-stimulated HaCaT cells, parnassin inhibited the expression of Th2-type chemokine CCL17 and CCL22 genes by suppressing JAK2 and p38 MAPK signaling kinases and their downstream transcription factor STAT1. Parnassin also significantly reduced the gene expression of TSLP and IL-31, which are pruritus-inducing cytokines. These findings suggested that parnassin alleviates AD-like lesions via its immunomodulatory effects and can be used as a candidate drug for the prevention and treatment of AD because it is safer than existing treatments.

The hidden sentinel of the skin: An overview on the role of interleukin-13 in atopic dermatitis

Recent evidence suggests that interleukin (IL)-13 is a crucial cytokine involved in the pathogenesis of atopic dermatitis (AD). It is a central driver of type-2 T-helper inflammation and is overexpressed in lesional skin of AD patients. Upon release in peripheral skin, IL-13 activates its receptors, recruits inflammatory cells, and modifies the skin microbiome. IL-13 also reduces the expression of epidermal barrier proteins and activates sensory nerve mediating the itch transmission signal. Novel therapeutics that target IL-13 seem to be efficacious and safe for the treatment of patients with moderate-to-severe AD. The aim of our manuscript is to review the role that IL-13 plays in AD immunopathogenesis.

Dupilumab for treatment of severe atopic dermatitis accompanied by lichenoid amyloidosis in adults: Two case reports

BACKGROUND

Lichenoid amyloidosis (LA) is a subtype of primary cutaneous amyloidosis characterized by persistent multiple groups of hyperkeratotic papules, usually on the lower leg, back, forearm, or thigh. LA may be associated with several skin diseases, including atopic dermatitis (AD). The treatment of LA is considered to be difficult. However, as there is some overlap in the etiopathogenesis of LA and AD, AD treatment may also be effective for LA.

CASE SUMMARY

Case 1: A 70-year-old man was diagnosed with severe AD with LA based on large dark erythema and papules on the trunk and buttocks and dense hemispherical millet-shaped papules with pruritus on the extensor side of the lower limbs. He had a long history of the disease (8 years), with repeated and polymorphic skin lesions. Given the poor efficacy of traditional treatments, this patient was recommended to receive dupilumab treatment. At the initial stage, 300 mg was injected subcutaneously every 2 wk. After 28 wk, the drug interval was extended to 1 mo due to the pandemic. Follow-up observations revealed that the patient reached an Eczema Area Severity Index of 90 (skin lesions improved by 90% compared with the baseline) by the end of the study. Moreover, Investigator's Global Assessment score was 1, and scoring atopic dermatitis index and numeric rating scale improved by 97.7% and 87.5% compared with the baseline, respectively, with LA skin lesions having largely subsided. Case 2: A 30-year-old woman was diagnosed with severe AD with LA, due to dense and substantial papules on the dorsal hands similar to changes in cutaneous amyloidosis, and erythema and papules scattered on limbs and trunk with pruritus, present for 25 years. After 16 wk of dupilumab treatment, she stopped, and skin lesions completely subsided, without recurrence since the last follow-up.

CONCLUSION

Dupilumab shows rational efficacy and safety in the treatment of severe AD with LA, in addition to benefits in the quality of life of the patients.

Betulin and Its Derivatives Reduce Inflammation and COX-2 Activity in Macrophages

Betulin is a heavily studied natural compound for its use as an anticancer or pro-regenerative agent. The structural similarity between betulin to steroids gives rise to the idea that the substance may as well act as an anti-inflammatory drug. This study is the first to describe the anti-inflammatory properties of betulinic acid, betulin, and its derivatives with amino acids 1,4-diaminebutane (Dab), 1,3-diaminepropane (Dap), Ornithine (Orn), and lysine (Lys) on murine macrophages from lymphoma site. The compounds were compared to dexamethasone. To establish the response of the macrophages to the natural compounds, we tested the viability as well as sensitivity to the inflammatory signaling (IFNγR). IL-6 secretory properties and HSP-70 content in the cells were examined. Furthermore, we characterized the effects of compounds on the inhibition of cyclooxygenase-2 (COX-2) activity both in the enzymatic assays and molecular docking studies. Then, the changes in COX-2 expression after betulin treatment were assessed. Betulin and betulinic acid are the low-cytotoxicity compounds with the highest potential to decrease inflammation via reduced IL-6 secretion. To some extent, they induce the reorganization of IFNγR with nearly no effect on COX-2 activity. Conversely, Bet-Orn and Bet-Lys are highly cytotoxic and induce the aggregation of IFNγR. Besides, Bet-Lys reduces the activity of COX-2 to a higher degree than dexamethasone. Bet-Orn is the only one to increase the HSP-70 content in the macrophages. In case of IL-6 reduction, all compounds were more potent than dexamethasone.

Effects of Dupilumab on Itch-Related Events in Atopic Dermatitis: Implications for Assessing Treatment Efficacy in Clinical Practice

Dupilumab attenuates itch and skin inflammation in patients with atopic dermatitis (AD). However, itch-related events that are improved by dupilumab remain unclear. Therefore, the present study investigated changes in clinical scores, serum biomarkers, and the number of intraepidermal nerve fibers (IENFs) using skin biopsies and blood samples from 12 patients with moderate to severe AD before and after treatment with dupilumab. Clinical manifestations were assessed using eczema area and severity index (EASI) and visual analogue scale (VAS) scores at baseline and after 8 and 16 weeks of treatment. Serum levels of total immunoglobulin E (IgE), thymus and activation-regulated chemokine (TARC), interleukin (IL)-4, IL-13, IL-22, and IL-31 were examined by electrochemiluminescence, chemiluminescent enzyme immunoassays, ProQuantum immunoassays, and enzyme-linked immunosorbent assays (ELISA) at baseline and after 8 and 16 weeks of treatment. In skin biopsies from AD patients at baseline and after 16 weeks of treatment, IENFs were examined immunohistochemically with the anti-protein gene product (PGP) 9.5 antibody. The dupilumab treatment significantly improved EASI and VAS scores and decreased serum levels of TARC, IgE, and IL-22, whereas those of IL-13 and IL-31, and the number of IENFs remained unchanged and those of IL-4 increased. VAS scores were positively correlated with serum TARC, IL-22, and IgE levels and the degree of epidermal thickening. Serum IL-31 levels were positively correlated with the number of IENFs. These results suggest that serum TARC, IL-22, and IgE levels and epidermal thickness are itch-related events associated with dupilumab treatment and that serum IL-31 levels may reflect the degree of IENF density in AD patients. Therefore, dynamic changes may be used to assess the efficacy of dupilumab treatment to treat itching and inflammation in patients with AD.

Molecular Mechanisms of Luteolin Against Atopic Dermatitis Based on Network Pharmacology and in vivo Experimental Validation

PURPOSE

To undercover the underlying mechanisms of luteolin against atopic dermatitis (AD), clinically characterized by recurrent eczematous lesions and intense itching, based on network pharmacology, molecular docking and in vivo experimental validation.

METHODS

TCMSP, STITCH and SwissTargetPrediction databases were utilized to screen the corresponding targets of luteolin. Targets related to AD were collected from DisGeNET, GeneCards and TTD databases. PPI network of intersection targets was constructed through STRING 11.0 database and Cytoscape 3.9.0 software. GO and KEGG enrichment analysis were performed to investigate the critical pathways of luteolin against AD. Further, the therapeutic effects and candidate targets/signaling pathways predicted from network pharmacology analysis were experimentally validated in a mouse model of AD induced by 2, 4-dinitrofluorobenzene (DNFB).

RESULTS

A total of 31 intersection targets were obtained by matching 151 targets of luteolin with 553 targets of AD. Among all, 20 core targets were identified by PPI network topology analysis, including IL-6, TNF, IL-10, VEGFA, IL-4, etc., and molecular docking indicated that luteolin binds strongly to these core targets. KEGG pathway enrichment analysis suggested that the intersected targets were significantly enriched in IL-17 signaling pathway, Th17 cell differentiation, Th1 and Th2 cell differentiation, JAK/STAT signaling pathway, etc. The in vivo experiment validated that luteolin could alleviate AD-like skin symptoms, as evidenced by the lower SCORAD score, the reduced infiltration of mast cells and the recovery of skin barrier function. Furthermore, luteolin restored immune balance by regulating the production of Th1/Th2/Th17-mediated cytokines, which were both the predicted core targets. Moreover, luteolin inhibited the phosphorylation of JAK2 and STAT3 in the lesional skin.

CONCLUSION

Together, the present study systematically clarifies the ameliorative effects and possible molecular mechanisms of luteolin against AD through the combination of network pharmacology and experimental validation, shedding light on the future development and clinical application of luteolin.

The Philosophy of Dermatopathology

Diagnostic pathology involves studying sample cells and tissues obtained from the specific lesions of interest [...].

An Altered Skin and Gut Microbiota Are Involved in the Modulation of Itch in Atopic Dermatitis

Skin and gut microbiota play an important role in the pathogenesis of atopic dermatitis (AD). An alteration of the microbiota diversity modulates the development and course of AD, e.g., decreased microbiome diversity correlates with disease severity, particularly in lesional skin of AD. Itch is a hallmark of AD with unsatisfying treatment until now. Recent evidence suggests a possible role of microbiota in altering itch in AD through gut-skin-brain interactions. The microbial metabolites, proinflammatory cytokines, and impaired immune response lead to a modulation of histamine-independent itch, disruption of epidermal barrier, and central sensitization of itch mechanisms. The positive impact of probiotics in alleviating itch in AD supports this hypothesis, which may lead to novel strategies for managing itchy skin in AD patients. This review summarizes the emerging findings on the correlation between an altered microbiota and gut-skin-brain axis in AD, especially in modulating itchy skin.

Peripheral itch sensitization in atopic dermatitis

Atopic dermatitis is a skin disorder caused by skin dryness and barrier dysfunction, resulting in skin inflammation and chronic itch (or pruritus). The pathogenesis of atopic dermatitis is thought to be initiated by a lowering of the itch threshold due to dry skin. This lowering of the itch threshold is at least partially due to the increase in intraepidermal nerve fibers and sensitization of sensory nerves by interleukin (IL)-33 produced and secreted by keratinocytes. Such skin is easily prone to itch due to mechanical stimuli, such as rubbing of clothing and chemical stimuli from itch mediators. In patients with atopic dermatitis, once itch occurs, further itch is induced by scratching, and the associated scratching breaks down the skin barrier. Disruption of the skin barrier allows entry into the epidermis of external foreign substances, such as allergens derived from house dust mites, leading to an increased induction of type 2 inflammatory responses. As a result, type 2 cytokines IL-4, IL-13, and IL-31 are mainly secreted by Th2 cells, and their action on sensory nerve fibers causes further itch sensitization. These sequences of events are thought to occur simultaneously in patients with atopic dermatitis, leading to a vicious itch-scratch cycle. This vicious cycle becomes a negative spiral that leads to disease burden. Therefore, controlling itch is essential for the treatment of atopic dermatitis. In this review, we summarize and discuss advances in the mechanisms of peripheral itch sensitization in atopic dermatitis, focusing on skin barrier-neuro-immune triadic connectivity.