Peripheral itch sensitization in atopic dermatitis

Comparative Efficacy of Ustekinumab and Guselkumab in Improving Itch in Severe Psoriasis Patients

BACKGROUND

Biologics effectively improve psoriatic skin lesions, but their impact on itch relief remains unclear.

OBJECTIVE

To evaluate itch improvement in severe psoriasis patients treated with ustekinumab or guselkumab.

METHODS

This retrospective study analyzed patients with severe psoriasis who completed initial efficacy evaluations after treatment with either biologic. Itch severity was assessed using numerical rating scale (NRS), visual analog scale, and verbal rating scale. NRS improvement was evaluated after three injections.

RESULTS

Among 108 patients (74 on ustekinumab, 34 on guselkumab), 77 (71.3%) had moderate-to-severe itch (NRS ≥4) at baseline. Of these, 63 (81.8%) achieved an NRS improvement of ≥4 points. Ustekinumab showed greater itch relief compared to guselkumab in NRS (p=0.033). On the other hand, guselkumab showed more reduction for psoriatic skin lesions than ustekinumab in the Psoriasis Area and Severity Index (p=0.040). In the moderate-to-severe itch group, patients with large plaques experienced significantly greater improvement in NRS than those with small plaques (p=0.012).

CONCLUSION

While guselkumab is generally preferred for psoriatic skin lesions, ustekinumab may provide superior itch relief.

Natural Turmeric-Derived Nanovesicles-Laden Metal-Polyphenol Hydrogel Synergistically Restores Skin Barrier in Atopic Dermatitis via a Dual-Repair Strategy

Skin barrier impairment is critical in the development of atopic dermatitis (AD), increasing vulnerability to external pathogens and disrupting cell metabolism, which leads to inflammatory stress and immune imbalance. In this study, a natural turmeric-derived nanovesicle (TDNV)-laden metal polyphenol hydrogel, termed Fe-HD@TDNV is proposed, to synergistically restore the compromised skin barrier in AD through a dual-repair strategy. The TDNV effectively regulates metabolic activity by upregulating the expression of skin barrier proteins, antioxidant enzymes, and antimicrobial peptides (AMPs) in keratinocytes, thereby reinforcing barrier integrity and combating pathogens. Simultaneously, the Fe-HD hydrogel, cross-linked by Fe3⁺ ions and hyaluronic acid-graft-dopamine (HD), provides superior skin compatibility and establishes a low oxidative stress environment for potentiating the therapeutic efficacy of TDNV. By improving skin barrier conditions, the Fe-HD@TDNV hydrogel exhibited desirable performance in maintaining better skin hydration, reducing epidermal thickness, and decreasing abnormal immune responses in acute skin disruption models and AD models. This work is expected to offer insights into the cross-kingdom regulation between plant-derived nanovesicles and mammals, as well as the design of disease-specific dual-functional repair strategies.

Long-term application of MC903 in mice prolongs the characteristic symptoms of atopic dermatitis, such as inflammation, skin barrier dysfunction, and itching

Atopic dermatitis (AD) is a chronic skin disease that causes itching and is characterized by recurrent flares and remissions. The interactions among type 2 inflammation, skin barrier dysfunction, and pruritus play important roles in the pathogenesis of AD. AD symptoms persist for a long period; thus, it is desirable to have disease models that reproduce a prolonged AD-like phenotype. Although MC903-induced AD model mice reportedly exhibit type 2 inflammation, skin barrier dysfunction, and pruritus, the effects of long-term application of MC903 on the changes in these symptoms over time are not fully understood. To clarify this point, we conducted a long-term time course analysis of these symptoms by applying MC903 to the ears of mice every other day for four weeks. Increased ear thickness, transepidermal water loss, number of scratching events, and serum IgE levels were observed in the MC903 model. Histological analysis revealed the infiltration of granulocytes and CD3-positive T cells and an increase in mast cells in the dermis. Furthermore, analyses of mRNA and protein expression in ear tissue revealed increased expression of thymic stromal lymphopoietin, IL-4, IL-13, and IL-33, which are involved in type 2 inflammation. All these changes were observed within two weeks after the initial application of MC903 and thereafter persisted throughout the experimental period. In conclusion, our data indicate that the long-term application of MC903 prolongs the duration of the three major symptoms of AD.

Psilocin alleviates acute itch in mice: possible involvement of 5-HT2A receptors and kynurenine pathway

We aimed to investigate whether psilocin, the bioactive metabolite of the well-known psychedelic, psilocybin, may have antipruritic effects in mice by interfering with the kynurenine pathway and interacting with 5-HT2A receptors. Eight mice were randomly assigned to each of the study groups receiving either normal saline, compound 48/80, psilocin (0.3, 1, and 3 mg/kg), or psilocin (1 mg/kg) + 1-MT (0.3 mg/kg). The scratching bouts were documented in each group. The hallucinogenic properties of psilocin were documented using the head-twitch response (HTR) test. To confirm their involvement, we also quantified the expression levels of TNF-α, TLR-4, indoleamine-2,3-dioxygenase (IDO), and 5-HT2A receptors across various study groups. We found that psilocin (1 mg/kg) exerted the most significant antipruritic and hallucinogenic effects (P < 0.0001). The activity of 5-HT2A receptors in the skin tissue of mice was confirmed by western blot. When psilocin (1 mg/kg) was given together with 1-MT (0.3 mg/kg), the antipruritic effects became more pronounced as compared to when psilocin was given alone (P < 0.05). TLR-4 and TNF-α expression levels considerably reduced after psilocin was applied, both alone and together with 1-MT (P < 0.05, P < 0.01, respectively). We also observed significantly decreased activity of IDO in the treatment groups (P < 0.05, P < 0.01 after giving psilocin alone, and together with 1-MT, respectively). To our knowledge, this is the first study to confirm the effectiveness of psychedelics in battling pruritus. Our findings offer a novel repositioning for psilocin. This may be particularly beneficial for psychological conditions accompanied by pruritus.

Neuroimmune mechanisms of type 2 inflammation in the skin and lung

Type 2 inflammation has a major role in barrier tissues such as the skin and airways and underlies common conditions including atopic dermatitis (AD) and asthma. Cytokines including interleukin 4 (IL-4), IL-5, and IL-13 are key immune signatures of type 2 inflammation and are the targets of multiple specific therapeutics for allergic diseases. Despite shared core immune mechanisms, the distinct structures and functions of the skin and airways lead to unique therapeutic responses. It is increasingly recognized that the nervous system has a major role in sensing and directing inflammatory processes. Indeed, crosstalk between type 2 immune activation and somatosensory functions mediates tissue-specific signatures such as itching in the skin. However, neuroimmune interactions are shaped by distinct neuronal and immune landscapes, and differ between the skin and airways. In the skin, dorsal root ganglia-derived neurons mediate pruritus via type 2 cytokines and neurogenic inflammation by mast cell or basophil activation. Conversely, vagal ganglia-derived neurons regulate airway immune responses by releasing neuropeptides/neurotransmitters such as calcitonin gene-related peptides, neuromedin U, acetylcholine, and noradrenaline. Sensory neuron-derived vasoactive intestinal peptide forms a feedback loop with IL-5, amplifying eosinophilic inflammation in the airways, a mechanism that is absent in the skin. These differences influence the efficacy of cytokine-targeted therapies. For instance, IL-4/IL-13-targeted therapies like dupilumab demonstrate efficacy in AD and allergic airway diseases, whereas IL-5-targeted therapies are effective in eosinophilic asthma but not AD. Understanding these neuroimmune interactions underscores the need for tailored therapeutic approaches to address allergic diseases where barrier tissues are involved.

Keloids and inflammation: the crucial role of IL-33 in epidermal changes

Introduction

Keloids are benign fibroproliferative disorders characterized by excessive collagen deposition and inflammation that extend beyond the original wound boundaries. IL-33 is an alarmin cytokine released upon cellular damage or stress. Dysregulation of IL-33 in epidermal keratinocytes compromises the skin barrier and triggers chronic inflammation.

Method

In this study, we first noticed an increased expression of IL-33 in the keratinocytes of keloid epidermis through histological staining. Then, an increased expression of IL-33 receptor (ST2) in the lymphocytes infiltrating the superficial dermis of keloid scars were identified through histological staining and flow cytometry analysis. The IFN-γ-IL-33 loop between lymphocytes and keratinocytes were further revealed by flow cytometry and Western blotting analysis. The abnormal keratinocyte differentiation in epiderm is mediated by IFN-γ-IL-33 loop were confirmed by in vitro studies in HaCaT cells via Western blotting analysis and immunofluorescence staining. Finally, the IFN-γ-IL-33 loop were also verified in cocultured peripheral blood mononuclear cells and HaCaT through ELISA analysis.

Results

Our results demonstrate that IL-33 levels are significantly elevated in the epidermis of keloid tissues, where it functions as an alarmin, promoting a chronic inflammatory response. We further reveal a feedback loop between IL-33 and interferon-gamma (IFN-γ), whereby IL-33 induces IFN-g production in lymphocytes, which in turn stimulates keratinocytes to produce more IL-33. This loop contributes to impaired keratinocyte differentiation and skin barrier dysfunction, exacerbating the inflammatory environment.

Discussion

By elucidating the role of the IL-33/ST2 axis in keloid formation, this research provides valuable insights into potential therapeutic targets for managing this challenging condition.

Pulsatilla koreana Nakai Extract Attenuates Atopic Dermatitis-like Symptoms by Regulating Skin Barrier Factors and Inhibiting the JAK/STAT Pathway

Atopic dermatitis is caused by various factors, including complex interactions between immune responses and imbalances in T helper cells. In order to resolve the side effects of steroid-based treatment and rapidly improve atopy symptoms, the development of preventive substances for new treatments and as food supplements is essential. Pulsatilla koreana Nakai (PKN) is traditionally used as an effective herbal medicine for pain relief, anti-inflammation, and edema, and dried PKN is boiled and drunk as a tea to prevent them; however, its effect on skin manifestations such as atopy are unclear. Therefore, we investigated the in vivo and in vitro effects of PKN extract on improving symptoms of atopy as a potential treatment. By evaluating dermatitis scores and conducting histopathological analysis in mice with Dermatophagoides farina-induced atopy-like pathology, we demonstrated that PKN extract alleviated atopy symptoms. Moreover, PKN extract restored a reduction in the protein levels of skin barrier-related factors in skin tissue. Through in vitro analysis, we examined the impact of PKN on JAK/STAT signaling in IL-4/IL-13-stimulated human keratinocytes and elucidated the mechanisms that suppress the levels of skin barrier factors and inflammation. PKN extract inhibited JAK/STAT phosphorylation stimulated by IL-4/IL-13. Furthermore, docking analysis of PKN constituents indicated binding to JNK1/2 and STAT3/6 and a subsequent inhibition of signal transduction. Therefore, this suggests that PKN extract has potential not only as a treatment but also as a food supplement to improve atopic dermatitis by strengthening skin barrier factors and inhibiting key signaling molecules.

Identification and Validation of the Potential Key Biomarkers for Atopic Dermatitis Mitochondrion by Learning Algorithms

Purpose

Atopic dermatitis (AD) is a common inflammatory skin condition characterized by erythema and pruritus. Its precise pathogenesis remains unclear, though factors such as genetic predisposition, autoantigen response, allergen exposure, infections, and skin barrier dysfunction are involved. Research suggests a correlation between AD and mitochondrial dysfunction, as well as oxidative stress in skin tissues.

Methods

 Skin sample datasets related to AD (GSE36842, GSE120721, GSE16161, and GSE121212) were retrieved from the GEO database. Differential gene analysis identified differentially expressed genes (DEGs) in AD. Three potential biomarkers-COX17, ACOX2, and ADH1B-were identified using LASSO and Support Vector Machine (SVM) algorithms. These biomarkers were validated through ROC curve analysis, nomogram modeling, calibration curves, and real-time PCR. Immune infiltration analysis assessed correlations of the biomarkers. Additionally, single-cell analysis of the GSE153760 dataset identified nine cell clusters and confirmed expression patterns of the three hub genes.

Results

Differential analysis identified 150 upregulated and 367 downregulated genes. Enrichment analysis revealed significant pathways related to mitochondrial function, oxidative stress, and energy metabolism in skin samples from AD patients. Area under the curve (AUC) values for biomarkers COX17, ACOX2, and ADH1B were 1.000, 0.928, and 0.895, respectively, indicating strong predictive capacity. qPCR results showed COX17 was highly expressed in AD lesions, while ACOX2 and ADH1B were higher in normal skin, consistent with previous findings. Correlation analysis indicated ACOX2 and ADH1B were positively correlated with resting mast cells but negatively with activated T cells and NK cells, while COX17 showed a positive correlation with activated T cells and a negative correlation with resting mast cells.

Conclusion

This study suggests that the hub genes COX17, ACOX2, and ADH1B may serve as potential biomarkers in the pathogenesis of AD. These findings could provide insights for the treatment and prognosis of AD and related inflammatory skin conditions.

Prurigo nodularis and acquired perforating dermatosis in chronic kidney disease: Are they the same entity?

Prurigo nodularis has been reported in itchy chronic kidney disease (CKD) patients, particularly those with end-stage renal failure. Acquired perforating dermatitis associated with CKD and diabetes is a group of disorders in which dermal materials are eliminated through the epidermis and is characterized by itchy papules and nodules. We focus on the relationship between prurigo nodularis and acquired perforating dermatitis in CKD and provide data to support that both entities share many of the same clinical and histologic features. These cutaneous diseases are often underreported in this patient population, leading to inadequate treatment and suboptimal patient outcomes. Our review of the literature suggests a relationship between prurigo nodularis/acquired perforating dermatitis and CKD, presumably driven by uremic pruritus, changes in the renin-angiotensin-aldosterone system, a predisposing immune dysregulation with increased interleukin-31 expression, and opioid system imbalances. A variety of pharmacologic therapies may be efficacious. The use of the new targeted biologics for prurigo nodularis and whether they are also helpful for CKD and acquired perforating dermatitis are welcome.

Type 2 cytokine-JAK1 signaling is involved in the development of dry skin-induced mechanical alloknesis

BACKGROUND

Mechanical alloknesis (m-alloknesis) is itch hypersensitivity induced by normally innocuous stimuli. It is sometimes observed in dry skin based itch-related diseases such as atopic dermatitis (AD), and often triggers the vicious itch-scratch cycle. The acetone-ether and water (AEW) mouse model mimics dry skin-induced m-alloknesis, yet its underlying mechanism remains unclear. Janus kinase (JAK) inhibitors are used to treat AD, but their effects on m-alloknesis are not fully known.

OBJECTIVE

To reveal the effects of various oral JAK inhibitors on m-alloknesis and their action points, using AEW model.

METHODS

AEW model was prepared by treatment with a mixture of acetone-ether, and they were orally administrated a JAK1/2 inhibitor baricitinib, a selective JAK1 inhibitor abrocitinib, or a JAK2 selective inhibitor AZ960, and evaluated m-alloknesis score as the total number of scratching responses in 30 mechanical stimulations. To further elucidate the mechanism of action, IL-4, IL-13 or thymic stromal lymphopoietin (TSLP) or their neutralizing antibodies were also applied to mice. In addition, the levels of these cytokines in mouse skin were measured using multiple immunoassays.

RESULTS

All of JAK inhibitors effectively reduced m-alloknesis, with abrocitinib demonstrating the most significant inhibition. The neutralizing antibodies against IL-4, IL-13, and TSLP inhibited m-alloknesis in AEW mice. Intradermal administration of IL-4, IL-13, or TSLP induced m-alloknesis, and abrocitinib effectively mitigated each cytokine-induced response. Highly sensitive assays detected IL-4, IL-13, IL-31 and TSLP in AEW-treated skin, with TSLP levels significantly increased.

CONCLUSION

Type 2 cytokine-JAK1 signaling is involved in the development of m-alloknesis in dry skin.

Skin-Protective Performance of Alternative Stratum Corneum Formed by a Pseudo-Ceramide-Containing Steroid Lamellar Cream

Ceramides in the stratum corneum (SC) are important for epidermal barrier function. We previously developed a synthetic pseudo-ceramide for medical (SPCM)-containing steroid cream [SPCM (+)]. This cream forms films on the skin surface and exerts anti-inflammatory effects through steroids. However, the preventive effects of this cream on the disruption of the skin barrier remained unclear. Therefore, in this study, we aimed to evaluate the protective role of SPCM (+) cream against atopic dermatitis (AD)-associated protease allergens on the skin in recovery from barrier-broken skin. We used three-dimensional (3D) skin and mouse models of disrupted skin barriers to evaluate the protective effect of SPCM (+) cream against V8 protease produced by Staphylococcus aureus. In NC/Nga mice with itching caused by living mites, SPCM (+) cream was repeatedly applied once a day for 2 weeks, and scratching behaviour was assessed every week using the MicroAct system. In the 3D skin model, the SPCM (+) cream directly blocked SC degradation by V8 protease of S. aureus and suppressed the expression of interleukin-36 gamma. The application of SPCM (+) cream to mite-parasitised mice suppressed scratching, reduced elevated activity of skin proteases, and inhibited upregulation of thymic stromal lymphopoietin. These beneficial effects of SPCM (+) cream were not observed with steroid creams without SPCM. These results suggest that the SPCM (+) cream is effective in relieving inflammation and itching by protecting the skin from proteases and allergens through its lamellar structure. This cream may be a promising treatment option for skin barrier disorders including AD and xerosis.

Dual Inhibition of Mast Cells and Thymic Stromal Lymphopoietin Using a Novel Bispecific Antibody, CDX-622

BACKGROUND

Mast cells (MCs) respond to an array of allergens that drive allergic and inflammatory diseases. Stem cell factor (SCF), the ligand for the receptor KIT, is required for MC survival and function. Thymic stromal lymphopoietin (TSLP) is an alarmin that promotes Type 2 inflammation in asthma and other inflammatory diseases. We describe CDX-622, a bispecific antibody (bsAb), that targets both SCF and TSLP to neutralize these distinct cytokines.

METHODS

The bsAb CDX-622 was developed from novel antagonist monoclonal antibodies (mAbs) to SCF (SCF-12) and TSLP (1D10). CDX-622 encodes the full-length 1D10 mAb and the single-chain variable fragment of SCF-12, linked to the C-terminus of the 1D10 heavy chain. CDX-622 was modified to prevent Fcγ receptor interactions and enhance FcRn binding. CDX-622 was tested using in vitro assays of MC and dendritic cell (DC) activation, an ex vivo human skin model, and in vivo studies in nonhuman primates.

RESULTS

Novel SCF and TSLP mAbs with neutralizing activity were generated. The bsAb CDX-622 potently inhibited SCF-driven MC degranulation and TSLP-mediated CCL17 release by DCs. In human skin samples treated with SCF and TSLP, CDX-622 markedly reduced proinflammatory, MC, and DC-related RNA signatures. Additionally, CDX-622 and SCF-12 mAb administered to cynomolgus macaques (Macaca fascicularis) had a profound effect on MCs without any observed toxicity.

CONCLUSIONS

CDX-622 is a potent inhibitor of MCs through the neutralization of SCF and effectively blocks Type 2 inflammatory responses driven by TSLP. Dual inhibition of these cytokines may lead to improved clinical outcomes in certain inflammatory disorders.

Flavonoids as Natural Anti-Inflammatory Agents in the Atopic Dermatitis Treatment

Eczema is a complex autoimmune condition characterised mainly by inflammation and skin lesions along with physical and psychological comorbidities. Although there have been significant advances in understanding the mechanisms behind atopic dermatitis, conventionally available treatments yield inconsistent results and have some unintended consequences. In today's digital age, where knowledge is just a click away, natural-based supplements have been on the rise for a more "natural" treatment towards any type of disease. Natural compounds, particularly derived from medicinal plants, have piqued significant interest in the development of herbal remedies for chronic inflammatory skin conditions. Among many compounds, flavonoids have shown promise in treating eczema due to their strong anti-inflammatory, antioxidant, and anti-allergic properties, making them helpful in preventing allergic reactions, inflammation, and skin irritation. This review highlights the therapeutic potential of flavonoid-based bioactive compounds to manage eczema, emphasising the mechanisms of action. Additionally, providing a comprehensive analysis of the potential of emerging and established compounds, while bridging a gap between traditional and modern medicine. Flavonoids offer a variety of opportunities for further research and innovative formulations that can maximise its full benefits. Further combination of flavonoids with various approaches such as nanoencapsulation for enhanced bioavailability, hydrogel-based delivery systems for a controlled release, and additive manufacturing for personalised topical formulations, could align with future precision medicine needs.

Efficacy and Safety of Nemolizumab in Patients With Prurigo Nodularis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

This meta-analysis evaluated the efficacy and safety of nemolizumab in treating prurigo nodularis through a systematic review of randomized controlled trials. A comprehensive literature search was conducted across multiple databases, including PubMed, Embase, Cochrane Library, and Web of Science, identifying relevant studies until January 5th 2025. Four randomized controlled trials involving 859 participants were included in the final analysis. The primary outcomes assessed were itching response measured by the Worst Itch Numeric Rating Scale (WI-NRS) and Investigator's Global Assessment (IGA) success. Nemolizumab demonstrated significant improvement in itch response compared to control, with a risk ratio of 3.52 (95% CI: 2.48 to 5.02, p < 0.00001) and low heterogeneity (I² = 28%). Similarly, IGA success rates were notably higher in the nemolizumab group, with a risk ratio of 4.40 (95% CI: 2.86 to 6.75, p < 0.00001) and low heterogeneity (I² = 11%). While adverse events were slightly more frequent in the nemolizumab group, the difference was not statistically significant (RR: 1.11, 95% CI: 0.99 to 1.24). The analysis was limited by the small number of included trials, relatively short follow-up periods, and lack of subgroup analysis. Despite these limitations, the findings suggest that nemolizumab is an effective and well-tolerated treatment for prurigo nodularis. Further research with longer follow-up periods and larger, more diverse patient populations is recommended to establish the long-term efficacy and safety profile of nemolizumab in treating this condition.

Baicalein ameliorates chronic itch in ACD mice by suppressing the spinal astrocytic STAT3-LCN2 cascade

Chronic itch is a maladaptive and debilitating symptom in patients with allergic contact dermatitis (ACD), adversely affecting their quality of life. There is a lack of effective treatments for ACD-associated uncontrollable itch. In this study, we explored the antipruritic effects of baicalein (BE), a bioactive flavonoid extracted from the root of Scutellaria baicalensis Georgi, and the underlying mechanisms in alleviating chronic itch triggered by diphenylcyclopropenone (DCP) in a mouse model of ACD. The ACD mice were intraperitoneally injected with BE (5, 30, and 60 mg·kg-1·d-1) for 7 days during the DCP challenge phase. The results showed that DCP-treated mice exhibited severe spontaneous scratching behaviors that was reduced after BE injections in a dose-dependent manner accompanied by inhibition of spinal astrocyte activation. We observed that the spinal astrocytic STAT3-LCN2 cascade plays a crucial role in controlling the activation of astrocytes in chronic itch. Intrathecal injection of the STAT3 inhibitor AG490 or Lcn2 siRNA significantly reduced scratching behavior and astrocyte activation in ACD mice. Moreover, BE markedly attenuated the increased phosphorylation of STAT3 (p-STAT3) and LCN2 expression in the spinal cords of ACD mice and in lipopolysaccharide-stimulated primary spinal astrocytes. Altogether, BE relieved chronic itch by suppressing the spinal astrocytic STAT3-LCN2 cascade. These findings provide a potential avenue for the management of chronic itch. Schematic summary of the main findings illustrating that BE alleviates chronic itch through suppressing the spinal astrocytic STAT3-LCN2 cascade. Specifically, BE suppresses the expression of p-STAT3 to inhibit the reactive state of astrocytes in spinal dorsal horn, and then decreases the expression of astrocytic LCN2 to alleviate chronic itch in ACD mice.

Sunscreens in pigmentary disorders: time to revise the message

Current sunscreen messaging centres around skin cancer prevention, with an emphasis on mitigating the damaging effects of ultraviolet B (UVB) radiation. Darker skin is believed to be better protected against UVB owing to its higher melanin content, and therefore, this messaging has been largely targeted at people with lighter skin tones. This is reflected by low sunscreen use by people of darker skin types. However, visible light (VL) is now being appreciated as a culprit behind exacerbation of disorders of hyperpigmentation such as melasma and post-inflammatory hyperpigmentation (PIH) which is known to significantly impair quality of life (QoL) of those affected. The role of VL in melanogenesis is not well known to patients nor to dermatologists and is a missed opportunity in the management of pigmentary disorders. We propose that changing the terminology from 'sunscreen' to 'light protection' acknowledges the central role of VL in melanogenesis, underlining the importance of VL protection and making the messaging more inclusive for people of all skin colours.

Epidermal Mechanical Scratching-Induced ROS Exacerbates the Itch-Scratch Cycle through TRPA1 Activation on Mast Cells in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by the itch-scratch cycle. Itching, induced by irritants or allergens that stimulate pruriceptive neurons, triggers uncontrollable mechanical scratching, leading to epidermal barrier disruption, immune response activation, inflammatory mediator release, and further stimulation of pruritus conduction. Although oxidative stress and immune cells can exacerbate this cycle, the correlation between mechanical scratching, epidermal oxidative stress, and dermal mast cell activation in AD remains unclear. In this study, by examining clinical specimens of AD, establishing a 3-dimensional coculture system of HaCaT and LAD2 cells, and utilizing a mechanical scratching mouse model of AD, we found that ROS produced by mechanically stimulated HaCaT can activate TRPA1 on mast cells presenting tryptase. Implementing a free radical scavenger and TRPA1 inhibitor can inhibit mast cell activation and type II inflammatory response, thereby alleviating itching and skin lesions in AD. These results indicate that active oxygen scavenging combined with TRPA1 inhibition can inhibit the itch-scratch cycle, which may present a potential approach for treatment of AD.

Mechanisms of Itch in Atopic Dermatitis

Atopic dermatitis (AD) is a common inflammatory skin disease characterized by recurrent eczematous lesions and intense itch. The pathological mechanism of AD involves a complex interaction between skin barrier dysfunction and a predominantly T helper (Th) 2-skewed immune dysregulation. The dysfunctional skin barrier in AD enhances antigen penetration, exacerbating allergic reactions. Scratching further damages the skin barrier, worsens dryness and increases the release of pro-inflammatory mediators, perpetuating the itch-scratch cycle. Breaking this cycle with appropriate treatments is vital. Th2 cells secrete interleukin (IL)-4, IL-13 and IL-31 which play keys roles in AD pathogenesis. IL-31 directly induces pruritus, while IL-4 and IL-13 enhance itching. An increased density of intraepidermal nerve fibers has been observed in AD lesions in a disease-state-dependent manner. In normal skin, both semaphorin 3A (Sema3A; a nerve repulsion factor) and nerve growth factor (NGF; a nerve elongation factor) are expressed. However, in AD lesions, Sema3A expression decreases while NGF expression increases. These findings suggest that epidermal nerve density is regulated by a fine balance between Sema3A and NGF, with Sema3A playing a key role in itch sensitivity in AD. In healthy skin, Sema3A is produced during the early-stage of differentiation of keratinocytes and moves into the upper epidermis. The levels of Sema3A and the density of epidermal nerve fibers may vary depending on the disease state of AD. Our future research will focus on the regulatory mechanisms of Sema3A in skin, and potential clinical applications.

Practical Guide for Implementing Cryogenic Electron Microscopy Structure Determination in Dermatology Research

Cryogenic electron microscopy (cryo-EM) and cryogenic electron tomography allow determination of structures of biological macromolecules in their native state in solution at atomic or near-atomic resolution. Recent advances in cryo-EM, that is, the "resolution revolution," and the establishment of national centers for cryo-EM data collection have remarkably expanded its applicability to practically all areas of health-related research. In this methods review, we highlighted the basics of single-particle cryo-EM and its application in the research of macromolecules and macromolecular complexes related to dermatology. We further illustrated a few examples of how this approach can be incorporated into drug development and study.

Cough and itch: Common mechanisms of irritation in the throat and skin

Cough and itch are protective mechanisms in the body. Cough occurs as a reflex motor response to foreign body inhalation, while itch is a sensation that similarly evokes a scratch response to remove irritants from the skin. Both cough and itch can last for sustained periods, leading to debilitating chronic disorders that negatively impact quality of life. Understanding the parallels and differences between chronic cough and chronic itch may be paramount to developing novel therapeutic approaches. In this article, we identify connections in the mechanisms contributing to the complex cough and scratch reflexes and summarize potential shared therapeutic targets. An online search was performed using various search engines, including PubMed, Web of Science, Google Scholar, and ClinicalTrials.gov from 1983 to 2024. Articles were assessed for quality, and those relevant to the objective were analyzed and summarized. The literature demonstrated similarities in the triggers, peripheral and central nervous system processing, feedback mechanisms, immunologic mediators, and receptors involved in the cough and itch responses, with the neuronal sensitization processes exhibiting the greatest parallels between cough and itch. Given the substantial impact on quality of life, novel therapies targeting similar neuroimmune pathways may apply to both itch and cough and provide new avenues for enhancing their management.

Bacterial cellulose based gel of glycyrrhizic acid gel for atopic dermatitis: Design, optimization, in vitro and in vivo investigation

It has been evidenced that water retention effect is very important in the treatment of eczema and one carrier of medicines, bacterial cellulose is accordance with the demand. However, this carrier is seldomly used as the carrier of medicines due to its inertia structure unless modified. As glycyrrhizic acid is a naturally amphiphilic and triterpenoid compound with anti-inflammatory effects and is a potential compound for treating eczema and it is naturally amphiphilic, a characteristic that may make bacterial cellulose one suitable carrier of the glycyrrhizic acid delivery system. Therefore, the main purpose of this study is to prepare and evaluate glycyrrhizic acid hydrogels with no-modified bacterial cellulose as the carrier. The bacterial cellulose glycyrrhizic acid hydrogel was prepared by physical crosslinking method, and the formulation was optimized through single factor investigation and orthogonal experiment. The optimized hydrogel was characterized in vitro to evaluate the skin permeability, skin irritation and efficacy on DNCB induced acute eczema in mice. In vitro characterization data supported the formation of hydrogels. GA-BC hydrogel has good skin permeability and no obvious irritation to animal skin. GA-BC hydrogel can significantly promote the recovery of skin lesions and has a certain effect on eczema as compared with GA hydrogel.

[Mechanism of transduction of itch and strategy of treatment for itch]

Itch is an unpleasant sense to evoke desire to scratch skin. Itch not only disturbs daily lives, but also exacerbates inflammation in case of atopic dermatitis (AD). It had been thought that both itch and pain are transduced by the same neurons; however, it is now known that neutrons transducing either itch or pain are distinct. Moreover, TRP channels, a family of calcium channels, play an important role for transducing itch as well as pain, temperature, and pressure. Development of neuroscience and molecular biology has dramatically advanced our understanding of how itch is transduced in recent years. On the other hand, development of immunology has revealed that there exist several immune types in our host defense mechanism and that type 2 immune reaction is dominant in the pathogenesis of allergic diseases including AD. Although it had been already known that type 2 cytokines contribute to the pathogenesis of AD by binding to their receptors on both immune cells and tissue resident cells, it has been recently found that several type 2 cytokines directly transduce the itch signals by binding to peripheral nerves. Due to this discovery, we can understand more deeply the itch mechanism of AD and can develop molecularly targeted drugs for AD targeting type 2 cytokines, which has dramatically changed the treatment of AD. In this review article, we describe the progress of our recent understanding of the itch mechanism and the strategy of treatment against it.

Enoximone alleviates atopic dermatitis-like skin inflammation via inhibition of type 2 T helper cell development

Atopic dermatitis (AD) is an inflammatory skin disease that affects approximately 15-20 % of the children and 1-3 % of the adults worldwide. Corticosteroids and calcineurin inhibitors are used in AD therapy; however, they cause various side effects. Current studies focus on novel therapeutic targets such as phosphodiesterases (PDEs) to mitigate AD. However, the relationship between PDE3 inhibitors and AD has not yet been reported. This study aimed to investigate the therapeutic effects and pharmaceutical mechanisms of enoximone (Enox), a PDE3 inhibitor. Mice were stimulated with 2,4-dinitrochlorobenzene (DNCB) to induce AD-like skin inflammation and were topically treated with Enox for 2 weeks. Treatment with Enox reduced the dermatitis score, skin water loss, IgE production, and expression of cytokines and chemokines that were elevated by DNCB. Histologically, Enox treatment reduced the skin thickness and the infiltration of various inflammatory cells, including macrophages, mast cells, eosinophils, and type 2 T helper (Th2) cells. HuT78, a human T cell line, was used to investigate the differentiation of T cells into Th2 cells. Enox treatment decreased the expression of Th2 cytokines and GATA3, a Th2 cell marker in HuT78, and suppressed signaling pathways that play a crucial role in Th2 cell differentiation. Collectively, the results demonstrate that Enox alleviates AD-like skin inflammation by inhibiting T-cell development. Thus, Enox may be a therapeutic candidate for the treatment of AD.

Effects of Huang-Lian-Jie-Du decoction on improving skin barrier function and modulating T helper cell differentiation in 1-chloro-2,4-dinitrobenzene-induced atopic dermatitis mice

Background: Atopic dermatitis (AD) is among the most frequently encountered skin diseases, bothering a considerable number of patients. Today, corticosteroids and antihistamines are among the numerous drugs applied for the therapy of AD. However, lengthy use of them contributes to side effects, such as physiological changes in skin. As an alternative and supplementary therapy, traditional Chinese medicine has become a trend for AD treatment. Huang-Lian-Jie-Du decoction (HLJDD), a renowned herbal formula has been employed to treat inflammatory diseases such as AD. However, its role in regulating immunity in AD remains unclear. The object of this study was to elucidate the efficacy of HLJDD and reveal the implicit mechanism from an immunological perspective in AD-like mice. Methods: In brief, 1-chloro-2,4-dinitrobenzene (DNCB) for the sensitization phase (1% DNCB) and stimulation phase (1.5% DNCB) were applied for BALB/c mice. HLJDD and dexamethasone (DXMS) were administered orally to the mice. Mice skin and spleens were collected to evaluate the efficacy of HLJDD. 16S rRNA sequencing was applied to evaluate the commensal microbiota changes in skin and fecal. In vitro, spleen CD4+ T cells and bone marrow-derived mast cells (BMMCs) were co-cultured to explore the modulation of HLJDD in T helper (Th) cells phenotyping. Results: HLJDD showcased a substantial amelioration in skin through the upregulation of FLG, LOR, AQP3, and reducing scratching behaviors in AD-like mice, Also, the quantity of infiltrated mast cells (MCs), pruritus-related mRNA were decreased. In addition, the expression of OX40/OX40L was decreased by HLJDD, which was critical in Th-cell phenotyping. With the treatment of HLJDD, Th1/Th2 and Th17/Treg ratios in AD-like mice became balanced. The structure of commensal microbiota in AD-like mice was affected by HLJDD. HLJDD could also improve the imbalance of Th17/Treg in vitro. Conclusion: HLJDD could improve the symptoms of AD-like mice by alleviating the scratching behaviors via decreased Th2 and pruritus-related mRNA expression. HLJDD also enhanced the relative diversity of skin microbiota and changed the structure of intestinal microbiota. An in-depth study found that HLJDD could balance the ratio of Th1/Th2, Th17/Treg in AD-like mice, and Th17/Treg in vitro by regulating the OX40/OX40L signaling pathway.

Integration of high-resolution mass spectrometry technology with molecular network analysis and systems biology techniques to elucidate the active ingredients and mechanisms of Shiduqing capsules

RATIONALE

Shiduqing Capsules, a well-known Chinese patent medicine, are widely used clinically for the treatment of pruritus. However, to date, there is a lack of research on its pharmacological substances and mechanisms of action.

METHODS

In the current study, the chemical components of Shiduqing Capsules were identified using UHPLC-QE-Orbitrap-MS technology. Molecular network analysis was employed to identify structurally similar compounds to the known chemical components. The potential molecular targets of the active ingredients were predicted using the SwissTargetPrediction website. The identified targets were further analyzed using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis through the DAVID database. Molecular docking was used to validate the network pharmacology results.

RESULTS

Ultimately, A total of 51 chemical components of Shiduqing Capsules were identified. Molecular network analysis identified 21 flavonoids and 13 terpenoids. The core targets of these ingredients include TP53, AKT1, and STAT3. GO and KEGG enrichment analysis revealed 1,371 different biological functions and 177 signaling pathways. Molecular docking confirmed the high affinity between multiple core active ingredients of Shiduqing Capsules and pruritus targets.

CONCLUSION

In conclusion, the effective ingredients of Shiduqing Capsules exert a multifaceted therapeutic effect on pruritus through multiple targets and pathways.

Efficacy and Potential Mechanisms of Naringin in Atopic Dermatitis

Atopic dermatitis (AD) is one of the most prevalent chronic inflammatory skin diseases. Topical treatments are recommended for all patients regardless of severity, making it essential to develop an effective topical AD treatment with minimal side effects; We investigated the efficacy of topical application of naringin in AD and explored the possible mechanisms using an AD mouse model induced by 1-chloro-2,4-dinitrobenzene (DNCB). Clinical, histological, and immunological changes related to AD and Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling proteins in the skin tissues were measured as outcomes; Naringin treatment resulted in a significant improvement in dermatitis severity score and reduced epidermal thickness and mast cell count in the skin (p < 0.05). Naringin also demonstrated the ability to inhibit DNCB-induced changes in interleukin (IL) 4, chemokine (C-C motif) ligand (CCL) 17, CCL22, IL1β, interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α) levels by quantitative real-time polymerase chain reaction (qRT-PCR) and IL13 by enzyme-linked immunosorbent assay (ELISA) (p < 0.05). Western blot results exhibited the decreased JAK1, JAK2, STAT1, STAT3, phospho-STAT3, and STAT6 expression in the naringin-treated groups (p < 0.05); The findings of this study suggest that topical naringin may effectively improve the symptoms of AD and could be used as a therapeutic agent for AD.

Astrocyte-derived Interleukin-31 causes poor prognosis in elderly patients with intracerebral hemorrhage

The incidence of intracerebral hemorrhage (ICH) is increasing every year, with very high rates of mortality and disability. The prognosis of elderly ICH patients is extremely unfavorable. Interleukin, as an important participant in building the inflammatory microenvironment of the central nervous system after ICH, has long been the focus of neuroimmunology research. However, there are no studies on the role IL31 play in the pathologic process of ICH. We collected para-lesion tissue for immunofluorescence and flow cytometry from the elderly and young ICH patients who underwent surgery. Here, we found that IL31 expression in the lesion of elderly ICH patients was significantly higher than that of young patients. The activation of astrocytes after ICH releases a large amount of IL31, which binds to microglia through IL31R, causing a large number of microglia to converge to the hematoma area, leading to the spread of neuroinflammation, apoptosis of neurons, and ultimately resulting in poorer recovery of nerve function. Interfering with IL31 expression suppresses neuroinflammation and promotes the recovery of neurological function. Our study demonstrated that elderly patients release more IL31 after ICH than young patients. IL31 promotes the progression of neuroinflammation, leading to neuronal apoptosis as well as neurological decline. Suppression of high IL31 concentrations in the brain after ICH may be a promising therapeutic strategy for ICH.

Therapeutic Potential and Mechanisms of Mesenchymal Stem Cell and Mesenchymal Stem Cell-Derived Extracellular Vesicles in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic and inflammatory skin disease with intense itchiness that is highly prevalent worldwide.The pathogenesis of AD is complex and closely related to genetic factors, immunopathogenic factors, environmental factors, and skin infections. Mesenchymal stem cells (MSCs) are non-hematopoietic progenitor cells derived from the mesenchymal stroma. They have anti-inflammatory, anti-apoptotic, and regenerative properties. Numerous studies demonstrate that MSCs can play a therapeutic role in AD by regulating various immune cells, maintaining immune homeostasis, and promoting the repair of damaged tissues. The key mediators for their biological functions are extracellular vesicles (MSC-Evs) and soluble cytokines derived from MSCs. The safety and efficacy of MSCs have been demonstrated in clinical Phase I / IIa trials for AD. This paper provides a comprehensive review of the pathogenesis of AD and the currently published studies on the function of MSCs and MSC-Evs in AD, primarily including the pathogenesis and the immunomodulatory impacts of MSCs and MSC-Evs, along with advancements in clinical studies. It provides insights for comprehending AD pathogenesis and investigating treatments based on MSCs.

Anti-atopic dermatitis effect of fraxinellone via inhibiting IL-31 in vivo and in vitro

Chronic recurrent itch and skin inflammation are prominent features of atopic dermatitis (AD), which is closely related to the immune response driven by T-helper type 2 (Th2) cells. The expression of interleukin 31 (IL-31) is positively correlated with the severity of dermatitis. Anti-IL-31 receptor α (IL-31RA) targeted drugs have been used to treat AD, however, they are expensive and have side effects. Fraxinellone (FRA) is one of the main limonoid components in the dried root bark of Dictamnus dasycarpus Turcz.; however, its anti-inflammatory and antipruritic effects on atopic dermatitis (AD) have not been previously reported. In this study, we investigated the anti-dermatitis effect of FRA and its potential mechanism of action using a 2,4-dinitrofluorobenzene (DNFB)-induced AD-like mouse model and lipopolysaccharide (LPS)-stimulated HaCaT cells. FRA significantly inhibited chronic pruritus, epidermal thickening, and inflammatory infiltration in AD mice. FRA not only inhibited the levels of IL-31 in the serum and lesioned skin of AD mice but also significantly downregulated the mRNA expression and protein levels of IL-31, IL-31RA, transient receptor potential (TRP) V1, and TRPA1 in the lesioned skin and dorsal root ganglion (DRG) of AD mice. In LPS-stimulated HaCaT cells, FRA inhibited the production of iNOS and COX2, as well as the protein levels of IL-31, IL-31RA, TRPV1 and TRPA1, showing significant anti-inflammatory effects. In summary, our findings suggest that FRA exerts antipruritic and anti-inflammatory effects in AD by regulating the IL-31 pathway, and may hold promise for the clinical treatment of AD.

Commensal microbe regulation of skin cells in disease

Human skin is the host to various commensal microbes that constitute a substantial microbial community. The reciprocal communication between these microbial inhabitants and host cells upholds both the morphological and functional attributes of the skin layers, contributing indispensably to microenvironmental and tissue homeostasis. Thus, disruption of the skin barrier or imbalances in the microbial communities can exert profound effects on the behavior of host cells. This influence, mediated by the microbes themselves or their metabolites, manifests in diverse outcomes. In this review, we examine existing knowledge to provide insight into the nuanced behavior exhibited by the microbiota on skin cells in health and disease states. These interactions provide insight into potential cellular targets for future microbiota-based therapies to prevent and treat skin disease.

Mirogabalin inhibits scratching behavior of spontaneous model mouse of atopic dermatitis

Introduction: Atopic dermatitis (AD) is one of the most prevalent intractable chronic itch diseases worldwide. In recent years, new molecular-targeted drugs have emerged, but side effects and economic challenges remain. Therefore, since it is important for AD patients to have a wider range of treatment options, it is important to explore new therapeutic agents. Gabapentinoids, gabapentin and pregabalin, have been shown to be effective for the clinical treatment of several chronic itch. Recently, mirogabalin (MGB) was developed as a novel gabapentinoid. MGB is a drug for neuropathic pain and has a margin of safety between its side effects and the analgesic effect for animal experiments. Herein, we showed that MGB exhibited an antipruritic effect in a mouse model of AD using NC/Nga mice. Methods and results: The oral administration of MGB (10 mg/kg) inhibited spontaneous scratching behavior in AD mice and its effect was dose dependently. Then, when MGB (10 mg/kg) was orally administrated to healthy mice, it did not affect motor function, including locomotor activity, wheel activity, and coordinated movement. Moreover, gabapentin (100 mg/kg) and pregabalin (30 mg/kg), inhibited spontaneous scratching behavior in AD mice and decreased motor function in healthy mice. Furthermore, intracisternal injection of MGB (10 μg/site) significantly suppressed spontaneous scratching behavior in AD mice. Discussion: In summary, our results suggest that MGB exerts an antipruritic effect via the spinal dorsal horn using NC/Nga mice. We hope that MGB is a candidate for a novel therapeutic agent for AD with relatively few side effects.

Induction of Semaphorin 3A by Resveratrol and Pinostilbene via Activation of the AHR-NRF2 Axis in Human Keratinocytes

Semaphorin 3A (SEMA3A), a nerve-repellent factor produced by keratinocytes, has an inhibitory effect on nerve extension to the epidermis. Epidermal innervation is involved in pruritus in inflammatory skin diseases such as atopic dermatitis (AD) and dry skin. We previously reported that tapinarof, a stilbene molecule, upregulates SEMA3A in human keratinocytes. We also showed that this mechanism is mediated via the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, and the nuclear factor erythroid 2-related factor 2 (NRF2) axis. Since some stilbenes activate AHR and NRF2, we attempted to identify other stilbenes that upregulate SEMA3A. We analyzed normal human epidermal keratinocytes (NHEKs) treated with 11 types of stilbenes and examined SEMA3A expression. We found that resveratrol and pinostilbene, antioxidant polyphenols, upregulated SEMA3A and increased nuclear AHR and NRF2 expression. In addition, AHR knockdown by small interfering RNA (siRNA) transfection abolished the NRF2 nuclear expression. Furthermore, AHR and NRF2 knockdown by siRNA transfection abrogated resveratrol- and pinostilbene-induced SEMA3A upregulation. Finally, we confirmed that resveratrol and pinostilbene increased SEMA3A promoter activity through NRF2 binding using ChIP-qPCR analysis. These results suggest that resveratrol and pinostilbene upregulate SEMA3A via the AHR-NRF2 axis in human keratinocytes.

Region-specific activation in the accumbens nucleus by itch with modified scratch efficacy in mice - a model-free multivariate analysis

Itch is a protective/defensive function with divalent motivational drives. Itch itself elicits an unpleasant experience, which triggers the urge to scratch, relieving the itchiness. Still, it can also result in dissatisfaction when the scratch is too intense and painful or unsatisfactory due to insufficient scratch effect. Therefore, it is likely that the balance between the unpleasantness/pleasure and satisfaction/unsatisfaction associated with itch sensation and scratching behavior is determined by complex brain mechanisms. The physiological/pathological mechanisms underlying this balance remain largely elusive. To address this issue, we targeted the "reward center" of the brain, the nucleus accumbens (NAc), in which itch-responsive neurons have been found in rodents. We examined how neurons in the NAc are activated or suppressed during histamine-induced scratching behaviors in mice. The mice received an intradermal injection of histamine or saline at the neck, and the scratching number was analyzed by recording the movement of the bilateral hind limbs for about 45 min after injection. To experimentally manipulate the scratch efficacy in these histamine models, we compared histamine's behavioral and neuronal effects between mice with intact and clipped nails on the hind paws. As expected, the clipping of the hind limb nail increased the number of scratches after the histamine injection. In the brains of mice exhibiting scratching behaviors, we analyzed the expression of the c-fos gene (Fos) as a readout of an immediate activation of neurons during itch/scratch and dopamine receptors (Drd1 and Drd2) using multiplex single-molecule fluorescence in situ hybridization (RNAscope) in the NAc and surrounding structures. We performed a model-free analysis of gene expression in geometrically divided NAc subregions without assuming the conventional core-shell divisions. The results indicated that even within the NAc, multiple subregions responded differentially to various itch/scratch conditions. We also found different clusters with neurons showing similar or opposite changes in Fos expression and the correlation between scratch number and Fos expression in different itch/scratch conditions. These regional differences and clusters would provide a basis for the complex role of the NAc and surrounding structures in encoding the outcomes of scratching behavior and itchy sensations.

Atopic Dermatitis Itch: Scratching for an Explanation

Chronic pruritus is a cardinal symptom of atopic dermatitis (AD). The mechanisms underlying atopic itch involve intricate crosstalk among skin, immune components, and neural components. In this review, we explore these mechanisms, focusing on key players and interactions that induce and exacerbate itch. We discuss the similarities and differences between pruritus and pain in patients with AD as well as the relationship between pruritus and factors such as sweat and the skin microbiome. Furthermore, we explore novel targets that could provide significant itch relief in these patients as well as exciting future research directions to better understand atopic pruritus in darker skin types.

Effects of Psychological Stress on Spontaneous Itch and Mechanical Alloknesis of Atopic Dermatitis

Atopic dermatitis (AD), a chronic inflammatory skin disease, manifests as an intractable itch. Psychological stress has been suggested to play a role in the onset and worsening of AD symptoms. However, the pathophysiological relationships between psychological stressors and cutaneous manifestations remain unclear. To elucidate the mechanisms underlying the stress-related exacerbation of itch, we investigated the effects of water stress, restraint stress and repeated social defeat stress on itch-related scratching behaviour, mechanical alloknesis and dermatitis in male NC/Nga mice with AD-like symptoms induced by the repeated application of ointment containing Dermatophagoides farina body. NC/Nga mice with AD-like symptoms were subjected to water stress, restraint stress and repeated social defeat stress, and their scratching behaviour, sensitivity to mechanical stimuli (mechanical alloknesis) and severity of  dermatitis were evaluated. Social defeat stress+ Dermatophagoides farina body-treated mice exposed to stress showed slower improvements in or the exacerbation of AD-like symptoms, including dermatitis and itch. In the mechanical alloknesis assay, the mechanical alloknesis scores of social defeat stress+ Dermatophagoides farina body-treated mice exposed to stress were significantly higher than those of non-exposed social defeat stress+ Dermatophagoides farina body- and social defeat stress-treated mice. These results suggest that psychological stress delays improvements in dermatitis by exacerbating itch hypersensitivity in AD.

Similarities and differences in peripheral itch and pain pathways in atopic dermatitis

Atopic dermatitis (AD) is predominantly characterized by intense itching, but concomitant skin pain is experienced by more than 40% of patients. Patients with AD display considerable somatosensory aberrations, including increased nerve sensitivity to itch stimuli (hyperknesis), perception of itch from innocuous stimuli (alloknesis), or perception of pain from innocuous stimuli (allodynia). This review summarizes the current understanding of the similarities and differences in the peripheral mechanisms underlying itch and pain in AD. These distinct yet reciprocal sensations share many similarities in the peripheral nervous system, including common mediators (such as serotonin, endothelin-1, IL-33, and thymic stromal lymphopoietin), receptors (such as members of the G protein-coupled receptor family and Toll-like receptors), and ion channels for signal transduction (such as certain members of the transient receptor potential [TRP] cation channels). Itch-responding neurons are also sensitive to pain stimuli. However, there are distinct differences between itch and pain signaling. For example, specific immune responses are associated with pain (type 1 and/or type 3 cytokines and certain chemokine C-C [CCL2, CCL5] and C-X-C [CXCL] motif ligands) and itch (type 2 cytokines, including IL-31, and periostin). The TRP melastatin channels TRPM2 and TRPM3 have a role in pain but no known role in itch. Activation of μ-opioid receptors is known to alleviate pain but exacerbate itch. Understanding the connection between itch and pain mechanisms may offer new insights into the treatment of chronic pain and itch in AD.

Neuroimmune interplay during type 2 inflammation: Symptoms, mechanisms, and therapeutic targets in atopic diseases

Type 2 inflammation is characterized by overexpression and heightened activity of type 2 cytokines, mediators, and cells that drive neuroimmune activation and sensitization to previously subthreshold stimuli. The consequences of altered neuroimmune activity differ by tissue type and disease; they include skin inflammation, sensitization to pruritogens, and itch amplification in atopic dermatitis and prurigo nodularis; airway inflammation and/or hyperresponsiveness, loss of expiratory volume, airflow obstruction and increased mucus production in asthma; loss of sense of smell in chronic rhinosinusitis with nasal polyps; and dysphagia in eosinophilic esophagitis. We describe the neuroimmune interactions that underlie the various sensory and autonomic pathologies in type 2 inflammatory diseases and present recent advances in targeted treatment approaches to reduce type 2 inflammation and its associated symptoms in these diseases. Further research is needed to better understand the neuroimmune mechanisms that underlie chronic, sustained inflammation and its related sensory pathologies in diseases associated with type 2 inflammation.

Evaluation of Antioxidant Activity and Treatment of Eczema by Berberine Hydrochloride-Loaded Liposomes-in-Gel

In this paper, berberine hydrochloride-loaded liposomes-in-gel were designed and developed to investigate their antioxidant properties and therapeutic effects on the eczema model of the mouse. Berberine hydrochloride-liposomes (BBH-L) as the nanoparticles were prepared by the thin-film hydration method and then dispersed BBH-L evenly in the gel matrix to prepare the berberine hydrochloride liposomes-gel (BBH-L-Gel) by the natural swelling method. Their antioxidant capacity was investigated by the free radical scavenging ability on 2,2-diphenyl-1-picrylhydrazyl (DPPH) and H2O2 and the inhibition of lipid peroxides malondialdehyde (MDA). An eczema model was established, and the efficacy of the eczema treatment was preliminarily evaluated using ear swelling, the spleen index, and pathological sections as indicators. The results indicate that the entrapment efficiency of BBH-L prepared by the thin-film hydration method was 78.56% ± 0.7%, with a particle size of 155.4 ± 9.3 nm. For BBH-L-Gel, the viscosity and pH were 18.16 ± 6.34 m Pas and 7.32 ± 0.08, respectively. The cumulative release in the unit area of the in vitro transdermal study was 85.01 ± 4.53 μg/cm2. BBH-L-Gel had a good scavenging capacity on DPPH and H2O2, and it could effectively inhibit the production of hepatic lipid peroxides MDA in the concentration range of 0.4-2.0 mg/mL. The topical application of BBH-L-Gel could effectively alleviate eczema symptoms and reduce oxidative stress injury in mice. This study demonstrates that BBH-L-Gel has good skin permeability, excellent sustained release, and antioxidant capabilities. They can effectively alleviate the itching, inflammation, and allergic symptoms caused by eczema, providing a new strategy for clinical applications in eczema treatment.

Canine Atopic Dermatitis: Prevalence, Impact, and Management Strategies

Atopic dermatitis (AD) is a common inflammatory and pruritic allergic skin disease in humans and dogs worldwide. The pathogenesis of AD is multifactorial, immunologically complex, and may involve genetic factors, epidermal barrier dysfunction, microbiome changes, immune dysregulation, and allergic sensitization. Across species, prevalence of AD is on the rise. At present, there is no cure for canine AD (CAD). The treatment for CAD is multifaceted and aimed at controlling the pruritus, associated inflammation, and infections, repairing the skin barrier function, and dietary management. This review presents data on prevalence, impact, and complex immunological interactions in AD with a focus on subsequent management of the disease in the canine population. A multimodal approach for management of CAD to address varying clinical signs and responses to therapies is discussed.

The Role of the Gut Microbiome and Microbial Dysbiosis in Common Skin Diseases

Dermatoses are an increasingly common problem, particularly in developed countries. The causes of this phenomenon include genetic factors and environmental elements. More and more scientific reports suggest that the gut microbiome, more specifically its dysbiosis, also plays an important role in the induction and progression of diseases, including dermatological diseases. The gut microbiome is recognised as the largest endocrine organ, and has a key function in maintaining human homeostasis. In this review, the authors will take a close look at the link between the gut-skin axis and the pathogenesis of dermatoses such as atopic dermatitis, psoriasis, alopecia areata, and acne. The authors will also focus on the role of probiotics in remodelling the microbiome and the alleviation of dermatoses.

The skin-brain connection and pleasant touch as supportive care for psychocutaneous disorders

Psychodermatology is a subdiscipline of dermatology at the intersection of dermatology, psychiatry, and psychology. In dermatology clinical practice, patients may present with skin disease that affects their mental health, or skin disorders induced or worsened by psychological/psychiatric problems so there is a need for specialised education of dermatologists, as well as multidisciplinary teams, to achieve better management of these patients. Understanding the interaction between the central nervous system and the skin underlying psychocutaneous disorders could help identify alternative therapies that may improve patient well-being. The concept of pleasurable touch has received increasing attention following the discovery of C-tactile (CT) fibres. While afferent C-fibre stimulation is usually associated with pain, temperature, or itch, CT-fibres are stimulated optimally by a stimulus not in the nociceptor range but by a gentle, low-force stroking. As this affective touch may counteract unpleasurable sensations, such as pain and itch, and elicit positive feelings, the potential benefits of gentle touch and massage are interesting for dermatological, especially psychocutaneous, disorders. Here we provide an overview of the skin-brain connection to help understand the benefits of touch and massage, as illustrated with studies on atopic dermatitis and burns, as an adjunct to dermatological treatment for improving patient well-being and optimising treatment outcomes.

KRT6A Inhibits IL-1β-Mediated Pyroptosis of Keratinocytes via Blocking IL-17 Signaling

Keratin 6A (KRT6A) is involved in the pathogenesis of various skin diseases. However, the reports on the roles of KRT6A in atopic dermatitis (AD) are limited. This study aimed to investigate the potentials of KRT6A in AD. mRNA levels were detected by RT-PCR. Cytokine release was determined by ELISA. Protein expression was determined using Western blot. Cell viability was determined by CCK-8. Cytotoxicity was detected by LDH assay. Cell death was determined by TUNEL. The pyroptosis of keratinocytes was detected using flow cytometry. We found that KRT6A was overexpressed in AD patients. Moreover, KRT6A was stimulated after exposed to proinflammatory cytokines. Overexpressed KRT6A suppressed inflammatory response, while KRT6A knockdown exerted the opposite effects. Overexpressed KRT6A suppressed inflammation-induced pyroptosis of keratinocytes. Additionally, KRT6A negatively regulated interleukin-17a (IL-17a) expression, blocking IL-17 signaling. IL-17a overexpression antagonized the effects of KRT6A and promoted pyroptosis of keratinocytes. In conclusion, KRT6A exerted protective functions in AD via regulating IL-17 signaling. This KRT6A/IL-17 may be a novel target for AD.

Cutaneous Components Leading to Pruritus, Pain, and Neurosensitivity in Atopic Dermatitis: A Narrative Review

Atopic dermatitis (AD) is a chronic, relapsing immunoinflammatory skin condition characterized by sensations such as pruritis, pain, and neuronal hypersensitivity. The mechanisms underlying these sensations are multifactorial and involve complex crosstalk among several cutaneous components. This review explores the role these components play in the pathophysiology of atopic dermatitis. In the skin intercellular spaces, sensory nerves interact with keratinocytes and immune cells via myriad mediators and receptors. These interactions generate action potentials that transmit pruritis and pain signals from the peripheral nervous system to the brain. Keratinocytes, the most abundant cell type in the epidermis, are key effector cells, triggering crosstalk with immune cells and sensory neurons to elicit pruritis, pain, and inflammation. Filaggrin expression by keratinocytes is reduced in atopic dermatitis, causing a weakened skin barrier and elevated skin pH. Fibroblasts are the main cell type in the dermis and, in atopic dermatitis, appear to reduce keratinocyte differentiation, further weakening the skin barrier. Fibroblasts and mast cells promote inflammation while dermal dendritic cells appear to attenuate inflammation. Inflammatory cytokines and chemokines play a major role in AD pathogenesis. Type 2 immune responses typically generate pruritis, and the type 1 and type 3 responses generate pain. Type 2 responses and increased skin pH contribute to barrier dysfunction and promote dysbiosis of the skin microbiome, causing the proliferation of Staphyloccocus aureus. In conclusion, understanding the dynamic interactions between cutaneous components in AD could drive the development of therapies to improve the quality of life for patients with AD.

MrgprA3+ Primary Sensory Neurons Mediate Acute Allergic Itch Responses in Atopic Dermatitis Model Mice

Itch is a prominent symptom of atopic dermatitis (AD). However, the underlying mechanism remains complex and has not yet been fully elucidated. Mas-related G protein-coupled receptor A3 (MrgprA3) has emerged attention as a marker of primary sensory neurons that specifically transmit itch signals; however, its involvement in AD-related itch has not been extensively explored. In this study, we developed an AD itch mouse model by repeatedly applying house dust mite (HDM) extract to barrier-impaired skin via a special diet. To clarify the role of MrgprA3+ neurons in itch behavior in our AD model, we adopted a toxin receptor-mediated cell knockout strategy using transgenic mice in which the diphtheria toxin receptor (DTR) gene was placed under the control of the Mrgpra3 promoter. When the HDM extract was repeatedly applied to the face and back skin of special diet-fed mice, the mice exhibited AD-like dry and eczematous skin lesions accompanied by three types of itch-related behaviors:1) spontaneous scratching, 2) acute scratching after antigen challenge, and 3) light touch-evoked scratching. Upon diphtheria toxin administration, substantial depletion of DTR+/MrgprA3+ neurons was observed in the dorsal root ganglion. Ablation of MrgprA3+ neurons suppressed acute itch responses after HDM application, whereas spontaneous and touch-evoked itch behaviors remained unaffected. Our findings unequivocally demonstrate that in our AD model, MrgprA3+ primary sensory neurons mediate acute allergic itch responses, whereas these neurons are not involved in spontaneous itch or alloknesis.

Anti-Inflammatory Effects of the LK5 Herbal Complex on LPS- and IL-4/IL-13-Stimulated HaCaT Cells and a DNCB-Induced Animal Model of Atopic Dermatitis in BALB/c Mice

Atopic dermatitis (AD) is a chronic inflammatory skin disease influenced by a complex interplay of genetic and environmental factors. The activation of the JAK-STAT pathway increases the expression of inflammatory cytokines such as IL-4 and IL-13, further deteriorating AD. Therefore, for the treatment of AD, the JAK-STAT pathway is emerging as a significant target, alongside inflammatory cytokines. This study investigates the potential therapeutic effects of a novel herbal complex, LK5, composed of Scutellaria baicalensis, Liriope platyphylla, Sophora flavescens, Dictammus dasycarpus, and Phellodendron schneider, known for their anti-inflammatory and immune-modulating properties. We examined the anti-inflammatory and anti-AD effects of the LK5 herbal complex in HaCaT cells stimulated by LPS and IL-4/IL-13, as well as in a mouse model of AD induced by DNCB. In HaCaT cells stimulated with LPS or IL-4/IL-13, the LK5 herbal complex demonstrated anti-inflammatory effects by inhibiting the expression of inflammatory cytokines including TNF-α, IL-6, and IL-1β, and downregulating the phosphorylation of STAT proteins. In a murine AD-like model induced by DNCB, administration of the LK5 herbal complex significantly ameliorated clinical symptoms, including dermatitis, ear thickness, and TEWL. Histological analysis revealed a reduction in epidermal thickness and mast cell infiltration. The LK5 herbal complex also inhibited pruritus induced by compound 48/80. Furthermore, the LK5 herbal complex treatment significantly decreased the levels of inflammatory cytokines such as TSLP, IL-6, and IgE in plasma and ear tissue of AD-induced mice. These findings suggest that the LK5 herbal complex may modulate the immune response and alleviate AD symptoms by inhibiting STAT pathways.

Physical influences on the skin barrier and pathogenesis of allergy

PURPOSE OF REVIEW

As the incidence of allergic conditions has increased in recent decades, the effects of climate change have been implicated. There is also increased knowledge on the effects of other physical influences, such as scratching and Staphylococcus aureus . The skin barrier is the first line of defense to the external environment, so understanding the ways that these factors influence skin barrier dysfunction is important.

RECENT FINDINGS

Although the impact on environmental exposures has been well studied in asthma and other allergic disorders, there is now more literature on the effects of temperature, air pollution, and detergents on the skin barrier. Factors that cause skin barrier dysfunction include extreme temperatures, air pollution (including greenhouse gases and particulate matter), wildfire smoke, pollen, scratching, S. aureus, and detergents.

SUMMARY

Understanding the ways that external insults affect the skin barrier is important to further understand the mechanisms in order to inform the medical community on treatment and prevention measures for atopic conditions.

Oncostatin M suppresses IL31RA expression in dorsal root ganglia and interleukin-31-induced itching

Background

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by intermittent itchy rash. Type 2 inflammatory cytokines such as interleukin (IL)-4, IL-13, and IL-31 are strongly implicated in AD pathogenesis. Stimulation of IL-31 cognate receptors on C-fiber nerve endings is believed to activate neurons in the dorsal root ganglion (DRG), causing itch. The IL-31 receptor is a heterodimer of OSMRβ and IL31RA subunits, and OSMRβ can also bind oncostatin M (OSM), a pro-inflammatory cytokine released by monocytes/macrophages, dendritic cells, and T lymphocytes. Further, OSM expression is enhanced in the skin lesions of AD and psoriasis vulgaris patients.

Objective

The current study aimed to examine the contributions of OSM to AD pathogenesis and symptom expression.

Methods

The expression levels of the OSM gene (OSM) and various cytokine receptor genes were measured in human patient skin samples, isolated human monocytes, mouse skin samples, and mouse DRG by RT-qPCR. Itching responses to various pruritogens were measured in mice by counting scratching episodes.

Results

We confirmed overexpression of OSM in skin lesions of patients with AD and psoriasis vulgaris. Monocytes isolated from the blood of healthy subjects overexpressed OSM upon stimulation with IL-4 or GM-CSF. Systemic administration of OSM suppressed IL31RA expression in the mouse DRG and IL-31-stimulated scratching behavior. In contrast, systemic administration of OSM increased the expression of IL-4- and IL-13-related receptors in the DRG.

Conclusion

These results suggest that OSM is an important cytokine in the regulation of skin monocytes, promoting the actions of IL-4 and IL-13 in the DRG and suppressing the action of IL-31. It is speculated that OSM released from monocytes in skin modulates the sensitivity of DRG neurons to type 2 inflammatory cytokines and thereby the severity of AD-associated skin itch.