Roles of Mast Cells in Cutaneous Diseases

Efficacy of Topical Palmitoylethanolamide (Levagen+) for the Management of Eczema Symptoms: A Double-Blind, Comparator-Controlled, Randomized Clinical Trial

INTRODUCTION

Eczema is a debilitating skin disorder clinically characterised by the development of itchy, dry, rough, and scaling skin caused by a series of rudimentary clinical phenotypes.

METHODS

This double-blind, randomised, comparator-controlled trial evaluated the effectiveness of topical application of a novel palmitoylethanolamide formulation (Levagen+) compared with a standard moisturiser (comparator) to reduce eczema severity and improve patient outcomes. Seventy-two participants aged over 18 years old with atopic eczema (symptoms including redness, dry skin, scaling, and/or itchiness) on their hands or arm were recruited. Participants were randomly allocated to one of two treatment groups (Levagen + or comparator). Treatment was applied to the affected area twice daily for 4 weeks. Outcome measures included Self-Assessed Eczema Area Severity Index (SA-EASI) scoring and Patient-Oriented Eczema Measure (POEM) from baseline to week 4.

RESULTS

Levagen+ was effective at alleviating symptom severity of eczema over 4 weeks. Levagen+ significantly reduced redness, dryness, and total POEM score compared to a comparator cream.

CONCLUSION

Levagen+ can significantly reduce eczema symptom severity compared to a comparator product, supporting its use as a potential treatment for eczema.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT05003453.

Beyond Allergies-Updates on The Role of Mas-Related G-Protein-Coupled Receptor X2 in Chronic Urticaria and Atopic Dermatitis

Mast cells (MCs) are an important part of the immune system, responding both to pathogens and toxins, but they also play an important role in allergic diseases, where recent data show that non-IgE-mediated activation is also of relevance, especially in chronic urticaria (CU) and atopic dermatitis (AD). Skin MCs express Mas-related G-protein-coupled receptor X2 (MRGPRX2), a key protein in non-IgE-dependent MC degranulation, and its overactivity is one of the triggering factors for the above-mentioned diseases, making MRGPRX2 a potential therapeutic target. Reviewing the latest literature revealed our need to focus on the discovery of MRGPRX2 activators as well as the ongoing vast research towards finding specific MRGPRX2 inhibitors for potential therapeutic approaches. Most of these studies are in their preliminary stages, with one drug currently being investigated in a clinical trial. Future studies and improved model systems are needed to verify whether any of these inhibitors may have the potential to be the next therapeutic treatment for CU, AD, and other pseudo-allergic reactions.

Inhibitory effects of catalpol on DNCB-induced atopic dermatitis and IgE-mediated mast cells reaction

Atopic dermatitis (AD) is a chronic, inflammatory cutaneous disease driven by immune dysregulation. Catalpol is an iridoids, possessing anti-inflammatory, antioxidant, and neuroprotective activities. It can be added to food as a dietary supplement. To evaluate the effects and mechanisms of catalpol on AD, both in vitro and in vivo studies were conducted. It was found that catalpol downregulated the phosphorylation of Lyn and Syk to inhibit various downstream pathways, including intracellular Ca2+ elevation, cytokines generation, and histamine release, which ultimately controlled mast cell (MCs) degranulation. The results showed that catalpol alleviated AD-like skin lesions and MC infiltration via regulation of pro-Th2 and Th2 cytokines in vivo. Furthermore, this compound reduced the levels of IgE in AD mice and improved allergic reactions in PCA mice. The results provided that catalpol was potentially developed as a dietary supplement to improve AD and other atopic diseases.

CREB Is Indispensable to KIT Function in Human Skin Mast Cells-A Positive Feedback Loop between CREB and KIT Orchestrates Skin Mast Cell Fate

Skin mast cells (MCs) are critical effector cells in acute allergic reactions, and they contribute to chronic dermatoses like urticaria and atopic and contact dermatitis. KIT represents the cells' crucial receptor tyrosine kinase, which orchestrates proliferation, survival, and functional programs throughout the lifespan. cAMP response element binding protein (CREB), an evolutionarily well-conserved transcription factor (TF), regulates multiple cellular programs, but its function in MCs is poorly understood. We recently reported that CREB is an effector of the SCF (Stem Cell Factor)/KIT axis. Here, we ask whether CREB may also act upstream of KIT to orchestrate its functioning. Primary human MCs were isolated from skin and cultured in SCF+IL-4 (Interleukin-4). Pharmacological inhibition (666-15) and RNA interference served to manipulate CREB function. We studied KIT expression using flow cytometry and RT-qPCR, KIT-mediated signaling using immunoblotting, and cell survival using scatterplot and caspase-3 activity. The proliferation and cycle phases were quantified following BrdU incorporation. Transient CREB perturbation resulted in reduced KIT expression. Conversely, microphthalmia transcription factor (MITF) was unnecessary for KIT maintenance. KIT attenuation secondary to CREB was associated with heavily impaired KIT functional outputs, like anti-apoptosis and cell cycle progression. Likewise, KIT-elicited phosphorylation of ERK1/2 (Extracellular Signal-Regulated Kinase 1/2), AKT, and STAT5 (Signal Transducer and Activator of Transcription) was substantially diminished upon CREB inhibition. Surprisingly, the longer-term interference of CREB led to complete cell elimination, in a way surpassing KIT inhibition. Collectively, we reveal CREB as non-redundant in MCs, with its absence being incompatible with skin MCs' existence. Since SCF/KIT regulates CREB activity and, vice versa, CREB is required for KIT function, a positive feedforward loop between these elements dictates skin MCs' fate.

Oat (Avena sativa L.) Sprouts Restore Skin Barrier Function by Modulating the Expression of the Epidermal Differentiation Complex in Models of Skin Irritation

Oats (Avena sativa L.) are used as therapeutic plants, particularly in dermatology. Despite numerous studies on their skin moisturization, anti-inflammation, and antioxidation effects, the precise molecular mechanisms of these effects are only partially understood. In this study, the efficacy of oat sprouts in the treatment of allergic contact dermatitis (ACD) was investigated, and their specific phytoconstituents and exact mechanisms of action were identified. In the in vivo ACD model, by stimulating the mitogen-activated protein kinase signaling pathway, oat sprouts increased the expression levels of proteins associated with skin barrier formation, which are produced during the differentiation of keratinocytes. In addition, in a lipopolysaccharide-induced skin irritation model using HaCaT, steroidal saponins (avenacoside B and 26-deglucoavenacoside B) and a flavonoid (isovitexin-2-o-arabinoside) of oat sprouts regulated the genetic expression of the same proteins located on the adjacent locus of human chromosomes known as the epidermal differentiation complex (EDC). Furthermore, oat sprouts showed immunomodulatory functions. These findings suggest the potential for expanding the use of oat sprouts as a treatment option for various diseases characterized by skin barrier disruption.

Synergism between IL-33 and MRGPRX2/FcεRI Is Primarily Due to the Complementation of Signaling Modules, and Only Modestly Supplemented by Prolonged Activation of Selected Kinases

Skin mast cells (MCs) express high levels of MRGPRX2, FcεRI, and ST2, and vigorously respond to their ligands when triggered individually. IL-33/ST2 also potently synergizes with other receptors, but the molecular underpinnings are poorly understood. Human skin-derived MCs were stimulated via different receptors individually or jointly in the presence/absence of selective inhibitors. TNF was quantified by ELISA. Signaling cascades were studied by immunoblot. TNF was stimulated by FcεRI ≈ ST2 > MRGPRX2. Surprisingly, neither FcεRI nor MRGPRX2 stimulation elicited NF-κB activation (IκB degradation, p65 phosphorylation) in stark contrast to IL-33. Accordingly, TNF production did not depend on NF-κB in FcεRI- or MRGPRX2-stimulated MCs, but did well so downstream of ST2. Conversely, ERK1/2 and PI3K were the crucial modules upon FcεRI/MRGPRX2 stimulation, while p38 was key to the IL-33-elicited route. The different signaling prerequisites were mirrored by their activation patterns with potent pERK/pAKT after FcεRI/MRGPRX2, but preferential induction of pp38/NF-κB downstream of ST2. FcεRI/MRGPRX2 strongly synergized with IL-33, and some synergy was still observed upon inhibition of each module (ERK1/2, JNK, p38, PI3K, NF-κB). IL-33's contribution to synergism was owed to p38 > JNK > NF-κB, while the partner receptor contributed through ERK > PI3K ≈ JNK. Concurrent IL-33 led to slightly prolonged pERK (downstream of MRGPRX2) or pAKT (activated by FcεRI), while the IL-33-elicited modules (pp38/NF-κB) remained unaffected by co-stimulation of FcεRI/MRGPRX2. Collectively, the strong synergistic activity of IL-33 primarily results from the complementation of highly distinct modules following co-activation of the partner receptor rather than by altered signal strength of the same modules.

Osteopathic Approach for Keloids and Hypertrophic Scars

The skin is a complex organ, a system that influences and is influenced by the body system, with different skin layers always mechano-biologically active. In the presence of a lesion that damages the dermis, the skin undergoes sensory, morphological, and functional alterations. The subsequent adaptation is the formation of scar tissue, following distinct and overlapping biological phases. For reasons not yet fully elucidated, some healing processes lead to pathological scars, from which symptoms such as pain, itching, and functional limitations are derived. Currently, there is no gold standard treatment that fully meets the needs of different scars and can eliminate any symptoms that the patient suffers. One such treatment is manual medicine, which involves direct manual approaches to the site of injury. Reviewing the phases that allow the skin to be remodeled following an injury, this article reflects on the usefulness of resorting to these procedures, highlighting erroneous concepts on which the manual approach is based, compared to what the current literature highlights the cicatricial processes. Considering pathological scar adaptations, it would be better to follow a gentle manual approach.

Role of Innate Immunity in Allergic Contact Dermatitis: An Update

Our understanding of allergic contact dermatitis mechanisms has progressed over the past decade. Innate immune cells that are involved in the pathogenesis of allergic contact dermatitis include Langerhans cells, dermal dendritic cells, macrophages, mast cells, innate lymphoid cells (ILCs), neutrophils, eosinophils, and basophils. ILCs can be subcategorized as group 1 (natural killer cells; ILC1) in association with Th1, group 2 (ILC2) in association with Th2, and group 3 (lymphoid tissue-inducer cells; ILC3) in association with Th17. Pattern recognition receptors (PRRs) including toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) in innate immune cells recognize damage-associated molecular patterns (DAMPs) and cascade the signal to produce several cytokines and chemokines including tumor necrosis factor (TNF)-α, interferon (IFN)-α, IFN-γ, interleukin (IL)-1β, IL-4, IL-6, IL-12, IL-13, IL-17, IL-18, and IL-23. Here we discuss the recent findings showing the roles of the innate immune system in allergic contact dermatitis during the sensitization and elicitation phases.

Mast cells in type 2 skin inflammation: Maintenance and function

Mast cells (MCs) are immune cells residing in tissues and playing indispensable roles in maintaining homeostasis and inflammatory states. Skin lesions associated with atopic dermatitis (AD) and type 2 skin inflammation display an increment in MCs, which have both pro- and anti-inflammatory effects. The direct and indirect activations of skin MCs by environmental factors such as Staphylococcus aureus can instigate type 2 skin inflammation in AD with poorly understood mechanisms. Furthermore, both IgE-dependent and -independent degranulation of MCs contribute to pruritus in AD. Conversely, MCs suppress type 2 skin inflammation by promoting Treg expansion through IL-2 secretion in the spleen. Moreover, skin MCs can upregulate gene expression involved in skin barrier function, thus mitigating AD-like inflammation. These functional variances of MCs in AD could stem from differences in experimental systems, their localization, and origins. In this review, we will focus on how MCs are maintained in the skin under homeostatic and inflammatory conditions, and how they are involved in the pathogenesis of type 2 skin inflammation.

In vitro and in vivo exploration of the anti-atopic dermatitis mechanism of action of Tibetan medicine Qi-Sai-Er-Sang-Dang-Song decoction

ETHNOPHARMACOLOGICAL RELEVANCE

Tibetan medicine Qi-Sai-Er-Sang-Dang-Song Decoction(QSD, ཆུ་སེར་སེང་ལྡེང་སུམ་ཐང་།)is a traditional Tibetan medical formulation with demonstrated clinical benefits in atopic dermatitis (AD). However, its potential mechanism and molecular targets remain to be elucidated.

AIM OF THE STUDY

This study aims to explore the activity and mechanism of QSD on AD in multiple dimensions by combining in vitro and in vivo experiments with network pharmacology.

MATERIALS AND METHODS

The AD effect of QSD was investigated by evaluating the levels of nitric oxide (NO) and interleukin-6 (IL-6) in the lipopolysaccharide (LPS) stimulated RAW264.7 cells. AD-like skin lesions in female BALB/c mice were induced by 2,4-dinitrochlorobenzene (DNCB). QSD or dexamethasone (positive control) were gavagely administered daily for 15 consecutive days. The body weight and skin lesion severity were recorded throughout the study. Enzyme-linked immunosorbent assay (ELISA) and Western blot (WB) analysis were used to illuminate the molecular targets associated with the anti-AD effects of QSD. Meanwhile, the ingredients of QSD in the blood were revealed and analyzed by Ultra performance liquid chromatography tandem quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) method. Network pharmacology was used to predict the targets and mechanism of active ingredient therapy for AD. In addition, the network pharmacology outcomes were further verified by molecular docking.

RESULT

After treatment with QSD, the levels of NO and IL-6 were decreased in the cell supernatant. Herein, QSD markedly decreased the eosinophil and mast cells infiltration in the dorsal skin of the 2,4-dinitrochlorobenzene. Moreover, QSD reconstructed the epidermal barrier by increasing the content of collagen fibers and changing the arrangement of DNCB-treated mice. QSD not only inhibited the levels of tumor necrosis factor-α (TNF-α) and interleukin-12 (IL-12) but also inhibited phosphorylation of p38, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) proteins in the dorsal skin. Four active ingredients were identified through UPLC-Q-TOF/MS, including (-)-epicatechin, kaempferol-7-O-glucoside, cassiaside, and questin. After the network pharmacological analysis, six core targets of QSD closely related to AD were obtained, including TNF-α, IL-6, Caspase-3 (CASP3), Epidermal growth factor (EGFR), Peroxisome proliferator-activated receptor gamma (PPARG), and Neurotrophic Receptor Tyrosine Kinase 1 (NTRK1). Meanwhile, through Gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment, the Mitogen-activated protein kinase (MAPK) signaling pathway occupies an important position in the QSD treatment of AD. The molecular docking results showed that the six core targets are stable in binding to the four active ingredients as indicated by the molecular docking results.

CONCLUSIONS

The anti-AD effect of QSD might be related to the reconstruction of the epidermal barrier and inhibition of inflammation, which regulated the MAPK pathway. Hence, it provided a promising idea for the study of Tibetan medicine prescriptions for the treatment of AD.

Resveratrol Protects against Skin Inflammation through Inhibition of Mast Cell, Sphingosine Kinase-1, Stat3 and NF-κB p65 Signaling Activation in Mice

Inflammation is pathogenic to skin diseases, including atopic dermatitis (AD) and eczema. Treatment for AD remains mostly symptomatic with newer but costly options, tainted with adverse side effects. There is an unmet need for safe therapeutic and preventative strategies for AD. Resveratrol (R) is a natural compound known for its anti-inflammatory properties. However, animal and human R studies have yielded contrasting results. Mast cells (MCs) are innate immune skin-resident cells that initiate the development of inflammation and progression to overt disease. R's effects on MCs are also controversial. Using a human-like mouse model of AD development consisting of a single topical application of antigen ovalbumin (O) for 7 days, we previously established that the activation of MCs by a bioactive sphingolipid metabolite sphingosine-1-phosphate (S1P) initiated substantial skin remodeling compared to controls. Here, we show that daily R application normalized O-mediated epidermal thickening, ameliorated cell infiltration, and inhibited skin MC activation and chemokine expression. We unraveled R's multiple mechanisms of action, including decreased activation of the S1P-producing enzyme, sphingosine kinase 1 (SphK1), and of transcription factors Signal Transducer and Activator of Transcription 3 (Stat3) and NF-κBp65, involved in chemokine production. Thus, R may be poised for protection against MC-driven pathogenic skin inflammation.

CREB Is Activated by the SCF/KIT Axis in a Partially ERK-Dependent Manner and Orchestrates Survival and the Induction of Immediate Early Genes in Human Skin Mast Cells

cAMP response element binding protein (CREB) functions as a prototypical stimulus-inducible transcription factor (TF) that initiates multiple cellular changes in response to activation. Despite pronounced expression in mast cells (MCs), CREB function is surprisingly ill-defined in the lineage. Skin MCs (skMCs) are critical effector cells in acute allergic and pseudo-allergic settings, and they contribute to various chronic dermatoses such as urticaria, atopic dermatitis, allergic contact dermatitis, psoriasis, prurigo, rosacea and others. Using MCs of skin origin, we demonstrate herein that CREB is rapidly phosphorylated on serine-133 upon SCF-mediated KIT dimerization. Phosphorylation initiated by the SCF/KIT axis required intrinsic KIT kinase activity and partially depended on ERK1/2, but not on other kinases such as p38, JNK, PI3K or PKA. CREB was constitutively nuclear, where phosphorylation occurred. Interestingly, ERK did not translocate to the nucleus upon SCF activation of skMCs, but a fraction was present in the nucleus at baseline, and phosphorylation was prompted in the cytoplasm and nucleus in situ. CREB was required for SCF-facilitated survival, as demonstrated with the CREB-selective inhibitor 666-15. Knock-down of CREB by RNA interference duplicated CREB's anti-apoptotic function. On comparison with other modules (PI3K, p38 and MEK/ERK), CREB was equal or more potent at survival promotion. SCF efficiently induces immediate early genes (IEGs) in skMCs (FOS, JUNB and NR4A2). We now demonstrate that CREB is an essential partaker in this induction. Collectively, the ancient TF CREB is a crucial component of skMCs, where it operates as an effector of the SCF/KIT axis, orchestrating IEG induction and lifespan.

Allergic Inflammation: Effect of Propolis and Its Flavonoids

The incidence of allergic diseases and their complications are increasing worldwide. Today, people increasingly use natural products, which has been termed a "return to nature". Natural products with healing properties, especially those obtained from plants and bees, have been used in the prevention and treatment of numerous chronic diseases, including allergy and/or inflammation. Propolis is a multi-component resin rich in flavonoids, collected and transformed by honeybees from buds and plant wounds for the construction and adaptation of their nests. This article describes the current views regarding the possible mechanisms and multiple benefits of flavonoids in combating allergy and allergy-related complications. These benefits arise from flavonoid anti-allergic, anti-inflammatory, antioxidative, and wound healing activities and their effects on microbe-immune system interactions in developing host responses to different allergens. Finally, this article presents various aspects of allergy pathobiology and possible molecular approaches in their treatment. Possible mechanisms regarding the antiallergic action of propolis on the microbiota of the digestive and respiratory tracts and skin diseases as a method to selectively remove allergenic molecules by the process of bacterial biotransformation are also reported.