Itch: Pathogenesis and treatment

Immune stimulus exposure as a trigger for the development of chronic pruritus and circulating blood type 2 inflammation

Background

Chronic pruritus (CP) is a poorly characterized condition associated with intense pruritus without a primary skin eruption. This condition tends to emerge more commonly in older adults, and there is limited research on triggering factors.

Objective

To explore the clinical characteristics and pathophysiology of CP following exposure to an immune stimulus.

Methods

Clinical characteristics and plasma samples were collected from 15 patients who developed CP following an immune stimulus such as checkpoint inhibitors or vaccination. A multiplex panel was used to analyze plasma cytokine concentrations within these patients.

Results

Most immunotherapy-treated patients experienced CP during treatment or after 21 to 60 days of receiving treatment, while vaccine-stimulated patients developed pruritus within a week of vaccination. Plasma cytokine analysis revealed elevated levels of 12 cytokines in patients with immune-stimulated CP compared to healthy controls. Notably, T helper 2 (Th2) related cytokines interleukin (IL)-5 (fold change 2.65; q < 0.25) and thymic stromal lymphopoietin (fold change 1.61 q < 0.25) were upregulated.

Limitations

Limitations of this study include limited sample size, particularly in the plasma cytokine assay.

Conclusions and Relevance

This study reveals triggers of CP development and describes alterations in blood Th2 markers in patients with CP, including IgE, increased blood eosinophils, and cytokines IL-5 and thymic stromal lymphopoietin.

Skin barrier: new therapeutic targets for chronic kidney disease-associated pruritus - a narrative review

The current incidence of chronic kidney disease-associated pruritus (CKD-aP) in patients with end-stage renal disease (ESRD) is approximately 70%, especially in those receiving dialysis, which negatively affects their work and private lives. The CKD-aP pathogenesis remains unclear, but uremic toxin accumulation, histamine release, and opioid imbalance have been suggested to lead to CKD-aP. Current therapeutic approaches, such as opioid receptor modulators, antihistamines, and ultraviolet B irradiation, are associated with some limitations and adverse effects. The skin barrier is the first defense in preventing external injury to the body. Patients with chronic kidney disease often experience itch due to the damaged skin barrier and reduced secretion of sweat and secretion from sebaceous glands. Surprisingly, skin barrier-repairing agents repair the skin barrier and inhibit the release of inflammatory cytokines, maintain skin immunity, and ameliorate the micro-inflammatory status of afferent nerve fibers. Here, we summarize the epidemiology, pathogenesis, and treatment status of CKD-aP and explore the possibility of skin barrier repair in CKD-aP treatment.

Efficacy and Safety of Abrocitinib in Prurigo Nodularis and Chronic Pruritus of Unknown Origin: A Nonrandomized Controlled Trial

Importance

Prurigo nodularis (PN) and chronic pruritus of unknown origin (CPUO) are chronic pruritic diseases that dramatically impair quality of life, but therapeutic options are limited. Abrocitinib, a Janus kinase 1 inhibitor, represents a promising therapy for both conditions.

Objective

To assess the efficacy and safety of 200-mg oral abrocitinib administered once daily in adults with moderate to severe PN or CPUO.

Design, Setting, and Participants

This phase 2, open-label, nonrandomized controlled trial conducted between September 2021 and July 2022 took place at a single center in the US. A total of 25 adult patients with moderate to severe PN or CPUO were screened. Ten patients with PN and 10 patients with CPUO were enrolled. All 20 patients completed the 12-week treatment period, 18 of whom completed the 4-week follow-up period.

Intervention

Abrocitinib, 200 mg, by mouth once daily for 12 weeks.

Main Outcomes and Measures

The primary efficacy end point was the percent change in weekly Peak Pruritus Numerical Rating Scale (PP-NRS) scores from baseline to week 12. Key secondary end points included the percentage of patients achieving at least a 4-point reduction in weekly PP-NRS score from baseline to week 12 and the percent change in Dermatology Life Quality Index (DLQI) scores.

Results

A total of 10 patients with PN (mean [SD] age, 58.6 [13.1] years; all were female) and 10 patients with CPUO (mean [SD] age, 70.7 [5.6] years; 2 were female) enrolled in the study. The mean (SD) baseline PP-NRS score was 9.2 (1.0) for PN and 8.2 (1.2) for CPUO. PP-NRS scores decreased by 78.3% in PN (95% CI, -118.5 to -38.1; P < .001) and 53.7% in CPUO (95% CI, -98.8 to -8.6; P = .01) by week 12. From baseline to week 12, 8 of 10 patients with PN and 6 of 10 patients with CPUO achieved at least a 4-point improvement on the PP-NRS. Both groups experienced significant improvement in quality of life as demonstrated by percent change in DLQI scores (PN: -53.2% [95% CI, -75.3% to -31.1%]; P = .002; CPUO: -49.0% [95% CI, -89.6% to -8.0%]; P = .02). The most common adverse event among patients was acneiform eruption in 2 of 20 patients (10%). No serious adverse events occurred.

Conclusions and Relevance

The results of this nonrandomized controlled trial suggest that abrocitinib monotherapy may be effective and tolerated well in adults with PN or CPUO. Randomized, double-blind, placebo-controlled trials are warranted to validate these findings.

Trial Registration

ClinicalTrials.gov Identifier: NCT05038982.

A Practical Approach to Diagnosing and Managing Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is an unpredictable inflammatory skin condition characterized by the spontaneous onset of itchy wheals, angioedema, or both, which occurs for longer than 6 weeks overall. Despite the relatively straightforward diagnostic algorithm for CSU, relying primarily on a detailed medical history and only limited laboratory tests, patients often wait years to be diagnosed, with many cycling through different healthcare practitioners before a diagnosis is made. Even then, current treatment options for CSU are limited, with approximately half of patients resistant to standard-of-care second-generation antihistamines at standard or higher doses. As such, there is an unmet need for improved, streamlined management for patients with CSU. Here, we review the evidence-based diagnostic algorithm for CSU, consider the required steps of the diagnostic workup, and provide practical, real-world advice on the management of CSU to improve the timely diagnosis and care of patients with this debilitating disease.

Prurigo nodularis: new insights into pathogenesis and novel therapeutics

Prurigo nodularis (PN) is an inflammatory skin condition characterized by intensely pruritic nodules on the skin. Patients with PN suffer from an intractable itch-scratch cycle leading to impaired sleep, psychosocial distress and a significant disruption in quality of life. The pathogenesis of PN is associated with immune and neural dysregulation, mediated by inflammatory cytokines [such as interleukin (IL)-4, -13, -17, -22 and -31] and neuropeptides (such as substance P and calcitonin gene-related peptide). There is a role for type 2 inflammation in PN in addition to T-helper (Th)17 and Th22-mediated inflammation. The neuroimmune feedback loop in PN involves neuropeptides released from nerve fibres that cause vasodilation and further recruitment of inflammatory cells. Inflammatory cells, particularly mast cells and eosinophils, degranulate and release neurotoxins, as well as nerve growth factor, which may contribute to the neuronal hyperplasia seen in the dermis of patients with PN and neural sensitization. Recent studies have also indicated underlying genetic susceptibility to PN in addition to environmental factors, the existence of various disease endotypes centred around degrees of type 2 inflammation or underlying myelopathy or spinal disc disease, and significant race and ethnicity-based differences, with African Americans having densely fibrotic skin lesions. Dupilumab became the first US Food and Drug Administration-approved therapeutic for PN, and there are several other agents currently in development. The anti-IL-31 receptor A inhibitor nemolizumab is in late-stage development with positive phase III data reported. In addition, the oral Janus kinase (JAK) 1 inhibitors, abrocitinib and povorcitinib, are in phase II trials while a topical JAK1/2 inhibitor, ruxolitinib, is in phase III studies.

Prurigo Nodularis: Pathogenesis and the Horizon of Potential Therapeutics

Chronic pruritus that lasts for over 6 weeks can present in various forms, like papules, nodules, and plaque types, with prurigo nodularis (PN) being the most prevalent. The pathogenesis of PN involves the dysregulation of immune cell-neural circuits and is associated with peripheral neuropathies, possibly due to chronic scratching. PN is a persistent and challenging condition, involving complex interactions among the skin, immune system, and nervous system. Lesional skin in PN exhibits the infiltration of diverse immune cells like T cells, eosinophils, macrophages, and mast cells, leading to the release of inflammatory cytokines and itch-inducing substances. Activated sensory nerve fibers aggravate pruritus by releasing neurotransmitters, perpetuating a vicious cycle of itching and scratching. Traditional treatments often fail, but recent advancements in understanding the inflammatory and itch transmission mechanisms of PN have paved the way for innovative therapeutic approaches, which are explored in this review.

The use of essential oils in atopic dermatitis: a review

Atopic dermatitis (AD) has become a common childhood disease that affects a large number of children worldwide and has become a chronic skin disease that causes huge economical and psychological damage to the whole family. Despite the use of steroids, immunosuppressants, and various topical preparation, the prognosis is still poor. Hence, this review aimed to explore the potential of using essential oils (EO) as an active ingredient in managing AD. The review was completed by using Pubmed, Scopus, and Medline to search for relevant articles that study the pathophysiology of AD, the properties of EO, the use of EO in managing AD, and the suitable advanced formulation to incorporate EO. From the review conducted, it was concluded that EO have huge potential in managing AD and can be used as complimentary therapeutic agents in AD treatment. Scientists and industries should venture into commercializing more topical products with EO to help manage AD more effectively.

The role of thymic stromal lymphopoietin in cutaneous disorders

Thymic Stromal Lymphopoietin (TSLP) is an important cytokine that invokes early immune responses. TSLP, an IL-7-like cytokine encoded by the TSLP gene, activates JAK1 and JAK2 signaling pathways, stimulating dendritic cells to induce inflammatory Th2 cells. This cytokine is associated with pruritus in various cutaneous disorders, particularly atopic dermatitis. Varying levels of the cytokine TSLP have been demonstrated in studies of different cutaneous disorders. Pharmacological treatment targeting TSLP has been explored recently, particularly in the realm of atopic dermatitis.This review explores the relation of TSLP to cutaneous diseases, highlighting its potential as a biomarker for monitoring disease progression in discoid lupus erythematosus (DLE). The pharmacological therapy involving TSLP is discussed, along with the potential role of TSLP promotion in the treatment of alopecia areata. This overview examines the background, structure, and functions of TSLP, with a focus on its association with cutaneous disorders and a special focus on the impact of the atopic march.

Spatial Mass Cytometry-Based Single-Cell Imaging Reveals a Disrupted Epithelial-Immune Axis in Prurigo Nodularis

Prurigo nodularis (PN) is a chronic, inflammatory skin condition that disproportionately affects African Americans and features intensely pruritic, hyperkeratotic nodules on the extremities and trunk. PN is understudied compared with other inflammatory skin diseases, with the spatial organization of the cutaneous infiltrate in PN yet to be characterized. In this work, we employ spatial imaging mass cytometry to visualize PN lesional skin inflammation and architecture with single-cell resolution through an unbiased machine learning approach. PN lesional skin has increased expression of caspase 3, NF-kB, and phosphorylated signal transducer and activator of transcription 3 compared with healthy skin. Keratinocytes in lesional skin are subdivided into CD14+CD33+, CD11c+, CD63+, and caspase 3-positive innate subpopulations. CD14+ macrophage populations expressing phosphorylated extracellular signal-regulated kinase 1/2 correlate positively with patient-reported itch (P = .006). Hierarchical clustering reveals a cluster of patients with PN with greater atopy, increased NF-kB+ signal transducer and activator of transcription 3-positive phosphorylated extracellular signal-regulated kinase 1/2-positive monocyte-derived myeloid dendritic cells, and increased vimentin expression (P < .05). Neighborhood analysis finds interactions between CD14+ macrophages, CD3+ T cells, monocyte-derived myeloid dendritic cells, and keratinocytes expressing innate immune markers. These findings highlight phosphorylated extracellular signal-regulated kinase-positive CD14+ macrophages as contributors to itch and suggest an epithelial-immune axis in PN pathogenesis.

Jiawei guomin decoction regulates the degranulation of mast cells in atopic dermatitis mice via the HIS/PAR-2 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Guomin decoction (GMD) is a traditional Chinese medicine commonly used in clinical practice. It has traditionally been used to treat all allergic diseases. Currently, Jiawei Guomin Decoction (JWGMD) is used to treat sensitive skin after initial therapy. Although it has a significant clinical therapeutic effect, the exact role of mast cell degranulation in treating atopic dermatitis (AD) is still unclear.

AIM OF THE STUDY

GMD and JWGMD can both treat allergic diseases, while JWGMD focuses on skin allergies. This study aims to explore the potential effect of JWGMD on the degranulation of mast cells in an AD mouse model induced by 2,4-dinitrofluorobenzene (DNFB) and investigate the effectiveness of JWGMD in alleviating disease progression to further provide specific therapeutic targets for treating AD.

MATERIALS AND METHODS

The scratching times and skin lesions of model mice induced by DNFB were observed, and skin tissues were collected for subsequent measurement. Histopathological changes in the back skin of mice were observed by haematoxylin eosin (H&E) staining, Toluidine blue staining was used to detect the degranulation of mouse skin mast cells, and the relationship between the expression of histamine (HIS), mast cell tryptase (MCT) and mast cell degranulation was analysed by enzyme-linked immunosorbent assay (ELISA). The expression of protease-activated receptor-2 (PAR-2), histamine 1 receptor (H1R), H2R, H4R and MCT proteins in AD mice was detected by Western blot (WB). Immunofluorescence assay (IFA) further confirmed the localization of PAR-2, H1R, H2R, H4R, and MCT proteins in the skin. Quantitative real-time PCR (qPCR) was used to determine PAR-2, H1R, H2R and H4R mRNA levels in skin lesions to further clarify the mechanism by which JWGMD amplifies mast cell degranulation in AD. In addition, a reliable ultrahigh-performance liquid chromatography-quadrupole electrostatic field orbitrap mass spectrometry (UPLC-QE-MS) nontargeted metabolomics analysis was performed to analyse the differences in metabolite abundance between GMD and JWGMD, and these results were used to identify the active components in JWGMD that may have antipruritic and anti-inflammatory properties and inhibit mast cell degranulation.

RESULTS

After intermittent stimulation with DNFB, the skin lesions showed extensive desquamation, dryness, scabbing, skin thickening, and slight bleeding. Both treatments alleviated this phenomenon and reduced the number of scratches, with JWGMD being the most effective. JWGMD can significantly reduce inflammatory cell infiltration, oedema, and some capillary neogenesis in mice and reduce the degranulation of mast cells. The ELISA results showed that JWGMD can increase the levels of MCT and HIS proteins. The WB and IFA results demonstrated that JWGMD reduced the expression levels of PAR-2, H1R, H4R, and MCT proteins in skin lesions, with protein localization mainly in the epidermal layer, while H2R protein levels were increased and mainly localized in the dermis. In addition, JWGMD downregulates the mRNA expression of PAR-2, H1R, H2R, and H4R. Interestingly, through UPLC-QE-MS nontargeted metabolomic analysis, we detected the anti-inflammatory and antiallergy active substances in JWGMD, such as methyl eugenol, dictamnine and sinapine.

CONCLUSIONS

JWGMD may alleviate itching through methyl syringol, dictamnine, sinapine and other substances, and its mechanism may be related to inhibiting the HIS/PAR-2 pathway in AD model mice and further regulating the self-amplification of mast cell degranulation. JWGMD is a potential drug for treating AD. Therefore, it deserves continuous attention and research.

ATF4 inhibits TRPV4 function and controls itch perception in rodents and nonhuman primates

ABSTRACT

Acute and chronic itch are prevalent and incapacitating, yet the neural mechanisms underlying both acute and chronic itch are just starting to be unraveled. Activated transcription factor 4 (ATF4) belongs to the ATF/CREB transcription factor family and primarily participates in the regulation of gene transcription. Our previous study has demonstrated that ATF4 is expressed in sensory neurons. Nevertheless, the role of ATF4 in itch sensation remains poorly understood. Here, we demonstrate that ATF4 plays a significant role in regulating itch sensation. The absence of ATF4 in dorsal root ganglion (DRG) neurons enhances the itch sensitivity of mice. Overexpression of ATF4 in sensory neurons significantly alleviates the acute and chronic pruritus in mice. Furthermore, ATF4 interacts with the transient receptor potential cation channel subfamily V member 4 (TRPV4) and inhibits its function without altering the expression or membrane trafficking of TRPV4 in sensory neurons. In addition, interference with ATF4 increases the itch sensitivity in nonhuman primates and enhances TRPV4 currents in nonhuman primates DRG neurons; ATF4 and TRPV4 also co-expresses in human sensory neurons. Our data demonstrate that ATF4 controls pruritus by regulating TRPV4 signaling through a nontranscriptional mechanism and identifies a potential new strategy for the treatment of pathological pruritus.

Pyromeconic acid-enriched Erigeron annuus water extract as a cosmetic ingredient for itch relief and anti-inflammatory activity

Erigeron annuus (EA), traditionally used to treat disorders such as diabetes and enteritis, contains a variety of chemicals, including caffeic acid, flavonoids, and coumarins, providing antifungal and antioxidative benefits. However, the ingredients of each part of the EA vary widely, and there are few reports on the functionality of water extracts in skin inflammation and barrier protection. We assessed the therapeutic properties of the extract of EA without roots (EEA) and its primary ingredient, pyromeconic acid (PA), focusing on their antihistamine, anti-inflammatory, and antioxidative capabilities using HMC-1(human mast cells) and human keratinocytes (HaCaT cells). Our findings revealed that histamine secretion, which is closely related to itching, was notably reduced in HMC-1 cells following pretreatment with EEA (0.1% and 0.2%) and PA (corresponding concentration, 4.7 of 9.4 µg/mL). Similarly, they led to a marked decrease in the levels of pro-inflammatory cytokines, including IL-1β, IL-8, IL-6, and IFN-γ. Furthermore, EA and PA enhanced antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT), reduced malondialdehyde (MDA) production, and showed reactive oxygen species (ROS) scavenging activity in HaCaT cells. Moreover, at the molecular level, elevated levels of the pro-inflammatory cytokines IL-1β, IL-6, TARC, and MDC induced by TNF-α/IFN-γ in HaCaT cells were mitigated by treatment with EEA and PA. We also revealed the protective effects of EEA and PA against SDS-induced skin barrier dysfunction in HaCaT cells by enhancing the expression of barrier-related proteins. Using NanoString technology, a comprehensive analysis of gene expression changes indicated significant modulation of autoimmune and inflammatory genes by EEA and PA. In summary, this study suggests that EEA and the corresponding concentration of PA as an active ingredient have functional cosmetic applications to alleviate itching and improve skin health.

Neuronal BST2: A Pruritic Mediator alongside Protease-Activated Receptor 2 in the IL-27-Driven Itch Pathway

Chronic itch is a common and complex symptom often associated with skin diseases such as atopic dermatitis (AD). Although IL-27 is linked to AD, its role and clinical significance in itch remain undefined. We sought to investigate IL-27 function in itch using tissue-specific transgenic mice, various itch models, behavior scoring, RNA sequencing, and cytokine/kinase array. Our findings show that IL-27 receptors were overexpressed in human AD skin. Intradermal IL-27 injection failed to directly induce itch in mice but upregulated skin protease-activated receptor 2 (PAR2) transcripts, a key factor in itch and AD. IL-27 activated human keratinocytes, increasing PAR2 transcription and activity. Coinjection of SLIGRL (PAR2 agonist) and IL-27 in mice heightened PAR2-mediated itch. In addition, IL-27 boosted BST2 transcription in sensory neurons and keratinocytes. BST2 was upregulated in AD skin, and its injection in mice induced itch-like response. BST2 colocalized with sensory nerve branches in AD skin from both human and murine models. Sensory neurons released BST2, and mice with sensory neuron-specific BST2 knockout displayed reduced itch responses. Overall, this study provides evidence that skin IL-27/PAR2 and neuronal IL-27/BST2 axes are implicated in cutaneous inflammation and pruritus. The discovery of neuronal BST2 in pruritus shed light on BST2 in the itch cascade.

The G protein-coupled estrogen receptor of the trigeminal ganglion regulates acute and chronic itch in mice

AIMS

Itch is an unpleasant sensation that severely impacts the patient's quality of life. Recent studies revealed that the G protein-coupled estrogen receptor (GPER) may play a crucial role in the regulation of pain and itch perception. However, the contribution of the GPER in primary sensory neurons to the regulation of itch perception remains elusive. This study aimed to investigate whether and how the GPER participates in the regulation of itch perception in the trigeminal ganglion (TG).

METHODS AND RESULTS

Immunofluorescence staining results showed that GPER-positive (GPER+ ) neurons of the TG were activated in both acute and chronic itch. Behavioral data indicated that the chemogenetic activation of GPER+ neurons of the TG of Gper-Cre mice abrogated scratching behaviors evoked by acute and chronic itch. Conversely, the chemogenetic inhibition of GPER+ neurons resulted in increased itch responses. Furthermore, the GPER expression and function were both upregulated in the TG of the dry skin-induced chronic itch mouse model. Pharmacological inhibition of GPER (or Gper deficiency) markedly increased acute and chronic itch-related scratching behaviors in mouse. Calcium imaging assays further revealed that Gper deficiency in TG neurons led to a marked increase in the calcium responses evoked by agonists of the transient receptor potential ankyrin A1 (TRPA1) and transient receptor potential vanilloid V1 (TRPV1).

CONCLUSION

Our findings demonstrated that the GPER of TG neurons is involved in the regulation of acute and chronic itch perception, by modulating the function of TRPA1 and TRPV1. This study provides new insights into peripheral itch sensory signal processing mechanisms and offers new targets for future clinical antipruritic therapy.

κ-Opioid receptor activation attenuates osteoarthritis synovitis by regulating macrophage polarization through the NF-κB pathway

Osteoarthritis (OA) is a prevalent and chronic joint disease that affects the aging population, causing pain and disability. Macrophages in synovium are important mediators of synovial inflammatory activity and pathological joint pain. Previous studies have demonstrated the significant involvement of κ-opioid receptor (KOR) in the regulation of pain and inflammation. Our study reveals a significant reduction in synovial KOR expression among patients and mice with OA. Here, we find that KOR activation effectively inhibits the expressions of the LPS-induced-inflammatory cytokines TNF-α and IL-6 by inhibiting macrophage M1 phenotype. Mechanistically, KOR activation effectively suppresses the proinflammatory factor secretion of macrophages by inhibiting the translocation of NF-κB into the nucleus. Our animal experiments reveal that activation of KOR effectively alleviates knee pain and prevents synovitis progression in OA mice. Consistently, KOR administration suppresses the expressions of M1 macrophage markers and the NF-κB pathway in the synovium of the knee. Collectively, our study suggests that targeting KOR may be a viable strategy for treating OA by inhibiting synovitis and improving joint pain in affected patients.

Interpreting the Relationship Among Itch, Sleep, and Work Productivity in Patients with Moderate-to-Severe Atopic Dermatitis: A Post Hoc Analysis of JADE MONO-2

BACKGROUND

Abrocitinib, an oral, once-daily Janus kinase 1-selective inhibitor, improved itch severity, sleep, and work productivity versus placebo in patients with moderate-to-severe atopic dermatitis.

OBJECTIVE

The aim of this study was to investigate relationships among itch, sleep, and work productivity in the phase III JADE MONO-2 clinical trial.

METHODS

A repeated-measures longitudinal model was used to examine relationships between itch (using the Peak Pruritus Numerical Rating Scale [PP-NRS] or Nighttime Itch Scale [NTIS]) and sleep disturbance/loss (using the Patient-Oriented Eczema Measure sleep item and SCORing AD Sleep Loss Visual Analog Scale) and, separately, between itch and work productivity (using the Work Productivity and Activity Impairment-Atopic Dermatitis Version 2.0 questionnaire). Mediation modelling was used to investigate the effect of treatment (abrocitinib vs placebo) on work impairment via improvements in itch and sleep.

RESULTS

The relationships between itch/sleep and itch/work productivity were approximately linear. PP-NRS scores of 0, 4-6, and 10 were associated with 0 days, 3-4 days, and 7 days per week of disturbed sleep, respectively. PP-NRS or NTIS scores of 0-1, 4-5, and 10 were associated with 0-10%, 20-30%, and >50% overall work impairment, respectively. Seventy-five percent of the effect of abrocitinib on reducing work impairment was indirectly mediated by improvement in itch, followed by sleep.

CONCLUSION

These results quantitatively demonstrate that reducing itch severity is associated with improvements in sleep and work productivity. Empirical evidence for the mechanism of action of abrocitinib showed that itch severity is improved, which reduces sleep loss/sleep disruption and, in turn, improves work productivity.

CLINICAL TRIAL REGISTRATION

NCT03575871.

Molecular mechanisms of pruritus in prurigo nodularis

Pruritus is the most common symptom of dermatological disorders, and prurigo nodularis (PN) is notorious for intractable and severe itching. Conventional treatments often yield disappointing outcomes, significantly affecting patients' quality of life and psychological well-being. The pathogenesis of PN is associated with a self-sustained "itch-scratch" vicious cycle. Recent investigations of PN-related itch have partially revealed the intricate interactions within the cutaneous neuroimmune network; however, the underlying mechanism remains undetermined. Itch mediators play a key role in pruritus amplification in PN and understanding their action mechanism will undoubtedly lead to the development of novel targeted antipruritic agents. In this review, we describe a series of pruritogens and receptors involved in mediating itching in PN, including cytokines, neuropeptides, extracellular matrix proteins, vasculogenic substances, ion channels, and intracellular signaling pathways. Moreover, we provide a prospective outlook on potential therapies based on existing findings.

Cholestatic Pruritus Mimicking a Cutaneous Drug Eruption

Pruritus, colloquially known as itch, is a common clinical symptom seen in a variety of dermatological conditions and systemic disorders. Pruritus can broadly be classified into four categories: neuropathic, neurogenic/systemic, psychogenic, and pruritoceptive. Initial categorization depends on anatomical and pathophysiological aspects of presentation and is reflective of underlying etiology. We report a case of an 83-year-old man presenting with generalized pruritus secondary to cholestasis from bile duct malignancy. This case is notable for atypical presenting features, including a trunk eruption comprised of excoriated papules with onset following meloxicam initiation, mimicking a cutaneous adverse drug reaction. Providers should consider systemic etiologies of pruritus in patients presenting with cutaneous eruptions with atypical features. Accurate categorization of pruritus can facilitate treatment and/or additional investigation of systemic disease.

Molecular Mechanisms of Cutaneous Immune-Related Adverse Events (irAEs) Induced by Immune Checkpoint Inhibitors

Over the past few decades, immune checkpoint inhibitors (ICIs) have emerged as promising therapeutic options for the treatment of various cancers. These novel treatments effectively target key mediators of immune checkpoint pathways. Currently, ICIs primarily consist of monoclonal antibodies that specifically block cytotoxic T-lymphocyte antigen 4 (CTLA-4), programmed cell death 1 (PD-1), programmed cell death-ligand 1 (PD-L1), and lymphocyte activation gene 3 protein (LAG-3). Despite the notable efficacy of ICIs in cancer treatment, they can also trigger immune-related adverse events (irAEs), which present as autoimmune-like or inflammatory conditions. IrAEs have the potential to affect multiple organ systems, with cutaneous toxicities being the most commonly observed. Although cutaneous irAEs are typically of low-grade severity and can usually be managed effectively, there are cases where severe irAEs can become life-threatening. Therefore, early recognition and a comprehensive understanding of the mechanisms underlying cutaneous irAEs are crucial for improving clinical outcomes in cancer patients. However, the precise pathogenesis of cutaneous irAEs remains unclear. This review focuses on the skin manifestations induced by ICIs, the prognosis related to cutaneous irAEs, and the exploration of potential mechanisms involved in cutaneous irAEs.

Estrogen alleviates acute and chronic itch in mice

Itching is associated with various skin diseases, including atopic dermatitis and allergic dermatitis, and leads to repeated scratching behavior and unpleasant sensation. Although clinical and laboratory research data have shown that estrogen is involved in regulating itch, the molecular and cellular basis of estrogen in itch sensation remains elusive. In the present study, it was found that estrogen-treated mice exhibited reduced scratching bouts when challenged with histamine, chloroquine, the proteinase-activated receptor-2 activating peptide SLIGRL-NH2 (SLIGRL), compound 48/80, and 5-hydroxytryptamine when compared with mice in the placebo group. Moreover, estrogen also suppressed scratching bouts in the mouse model of chronic itch induced by acetone-ether-water treatment. Notably, consistent with the behavioral tests, the present RNA-seq analysis showed that estrogen treatment caused significantly reduced expression levels of itch-related molecules such as Mas-related G-protein coupled receptor member A3, neuromedin B and natriuretic polypeptide b. In addition, estradiol attenuated histamine-induced and chloroquine-induced calcium influx in dorsal root ganglion neurons. Collectively, the data of the present study suggested that estrogen modulates the expression of itch-related molecules and suppresses both acute and chronic itch in mice.

Case report: Spinal cord stimulation in the treatment of pediatric erythromelalgia

Introduction

In children, erythromelalgia is a rare chronic pain syndrome characterized by erythema, severe burning pain, and itching of affected feet. Unfortunately, there is no definitive therapy available currently.

Case report

Here, we report a case of primary erythromelalgia and the treatment response in a 10-year-old boy, whose genetic findings for mutations in the SCN9A gene were positive and skin biopsy results were diagnosed as small fiber neuropathy, while he has suffered from excruciating burning pain, itching, erythema, and recurrent infections over the past 3 years. He did not respond well to conventional treatment, and the only way to receive minimal relief was to immerse his feet in ice water. After a successful trial of spinal cord stimulation (SCS), the implantable pulse generator (IPG) was successfully implanted without complications, and it proved partial response to therapy.

Conclusion

There is no specific, efficient treatment for pediatric erythromelalgia currently, but this case demonstrates neuromodulation serves as part of the multimodal regimen to treat pediatric erythromelalgia.

The association between pruritic dermatoses and inflammatory factors on sleep disorders: a cross-sectional study of the National Health and Nutrition Examination Survey (NHANES)

Pruritic dermatoses and sleep disorders have significant impacts on the health and quality of life of patients. Inflammatory conditions may lead to the sensation of itching. This study was to evaluate the association between pruritic dermatoses and inflammatory factors on sleep disorders. Data in the cross-sectional study were extracted from the National Health and Nutrition Examination Survey. The study population was divided into participants with and without sleep disorders. Pruritic dermatoses were assessed by the participant's self-report. Inflammatory factors included white blood cell count (WBC), lymphocyte count (LYM) and prognostic nutritional index (PNI). Logistic regression models were used with odds ratios and confidence intervals. The attributable proportion of interaction (AP) was utilized to assess the interaction between pruritic dermatoses and inflammatory factors on sleep disorders. Totally, 3,520 participants were included and 214 (6.08%) had sleep disorders. Pruritic dermatoses were associated with sleep disorders after adjusting for gender, age, race, marital status, body mass index, drinking, smoking, asthma, hay fever, allergy, depression and caffeine. LYM was associated with sleep disorders when inflammatory factors were divided by median. The interaction between participants without pruritic dermatoses and PNI < median on sleep disorders was observed compared to participants without pruritic dermatoses and PNI > median. Pruritic dermatoses were significantly associated with sleep disorders. We also found that a high level of PNI had an enhanced effect on the relationship between pruritic dermatoses and sleep disorders. Clinicians should focus on the potential sleep-related risks and changes in inflammatory factors in patients with pruritic dermatoses and intervene in time.

Endogenous Opioid Imbalance as a Potential Factor Involved in the Pathogenesis of Chronic Kidney Disease-Associated Pruritus in Dialysis Patients

Chronic pruritus is one of the most common symptoms of dermatological diseases. It may occur in the course of other disorders, such as kidney disease. Chronic kidney disease-associated pruritus (CKD-aP) most often affects people with end-stage renal disease. The etiology of this condition is still not fully understood, but researchers are currently focusing on a thorough analysis of the association between disturbed opioid balance and increased neuronal signaling leading to pruritus. The aim of this study is to assess the concentration of endogenous opioids in dialysis patients with and without pruritus and in the control group, and to determine the correlation between the concentration of these substances and the occurrence and severity of itching. The study involved 126 dialysis patients and 50 healthy controls. Patients were divided into groups with pruritus (n = 62) and without pruritus (n = 64). The severity of pruritus was assessed using the NRS scale. The concentration of endogenous opioids was determined using the ELISA. The concentration of met-enkephalin was higher in the group of patients with pruritus compared to the control group. Moreover, significantly lower levels of β-endorphin and dynorphin A were observed in the group of dialysis patients compared to the control group. In addition, a statistically significant difference was seen between the β-endorphin concentration in the group of dialysis patients with pruritus compared to the group without pruritus. The ratio of β-endorphin/dynorphin A concentrations was significantly lower in the group of patients with pruritus compared to patients without pruritus and the control group. No correlations were found between serum level of studied opioids and the severity of pruritus. The concentrations of the studied opioids did not correlate with the severity of pruritus. Observed opioid imbalance may affect the occurrence of CKD-aP in dialysis patients, but a thorough understanding of the mechanism of action of these substances in the sensation of pruritus is necessary to assess the possibility of finding a new therapeutic target.

Novel Insights into the Role of Keratinocytes-Expressed TRPV3 in the Skin

TRPV3 is a non-selective cation channel that is highly expressed in keratinocytes in the skin. Traditionally, keratinocytes-expressed TRPV3 is involved in multiple physiological and pathological functions of the skin, such as itching, heat pain, and hair development. Although the underlying mechanisms by which TRPV3 functions in vivo remain obscure, recent research studies suggest that several cytokines and EGFR signaling pathways may be involved. However, there have also been other studies with opposite results that question the role of TRPV3 in heat pain. In addition, an increasing number of studies have suggested a novel role of TRPV3 in promoting skin regeneration, indicating that TRPV3 may become a new potential target for regulating skin regeneration. This paper not only reviews the role of keratinocytes-expressed TRPV3 in the physiological and pathological processes of itching, heat pain, hair development, and skin regeneration, but also reviews the relationship between TRPV3 gene mutations and skin diseases such as atopic dermatitis (AD) and Olmsted syndrome (OS). This review will lay a foundation for further developing our understanding of the mechanisms by which TRPV3 is involved in itching, heat pain, and hair development, as well as the treatments for TRPV3-related skin diseases.

Itch and Janus Kinase Inhibitors

Itch is a common skin symptom, with complex aetiology and pathogenesis. It is mediated by 2 pathways, the histaminergic and non-histaminergic pathways. Chronic itch is understood to be processed by the latter and is difficult to treat with traditional pruritus therapies. The Janus kinase and signal transducer and activator of transcription pathway is a signalling mechanism that regulates gene expression through various cytokines. Janus kinase inhibitors, which have been tested and used for several autoimmune diseases, have also been shown to be effective for itch through clinical trials and case reports. Janus kinase inhibitors could be a good choice for pruritus in atopic dermatitis, psoriasis, and other diseases, such as prurigo nodularis and lichen planus, with rapid itch relief compared with conventional treatments. The most common adverse effects reported include nasopharyngitis, acne, and elevated blood creatine phosphokinase levels. Janus kinase inhibitors are currently prescribed with warnings about a potential increase in malignancies and cardiovascular diseases and usage in people of older ages. This review aims to provide knowledge about itch and the Janus kinase and signal transducer and activator of transcription pathway and to analyse the current evidence for itch relief by Janus kinase inhibitors.

Glial Cells and Itch: Possible Targets for Novel Antipruritic Therapies

Glial cells, which are the non-neuronal cells of the nervous system, play essential roles in brain development, homeostasis, and diseases. Glial cells have attracted attention because of their active involvement in many neurological disorders. In recent years, substantial progress has been made in our understanding of the roles of glial cells in the pathogenesis of itch. Mechanistically, central and peripheral glial cells modulate acute and chronic pruritus via different mechanisms. In this review, we present the current knowledge about the involvement of glial cells in the modulation of itch processing and the mechanism of glial cell activation under itch stimuli. Targeting glial cells may provide novel approaches for itch therapy.

Molecular docking, network pharmacology and experimental verification to explore the mechanism of Wulongzhiyangwan in the treatment of pruritus

Wulongzhiyangwan (WLZYW) is a Chinese prescription medicine for the treatment of pruritus, but its mechanism has not been clarified. The purpose of this study was to explore the mechanism of WLZYW in pruritus through network pharmacology analysis and experimental validation. The active components and corresponding targets of WLZYW were obtained from the Traditional Chinese Medicine Systematic Pharmacology (TCMSP) database. Pruritus-related targets were obtained from the GeneCards, TTD (Therapeutic Target Database), and DrugBank databases. The key compounds, core targets, main biological processes and signaling pathways related to WLZYW were identified by constructing and analyzing related networks. The binding affinity between WLZYW components and core targets was validated by AutoDock Vina software. In this study, RBL-2H3 cells were used to construct a degranulation model to simulate histamine-dependent pruritus. 10 chemical constituents, 235 targets and 3606 pruritus-related targets of WLZYW were obtained. Subsequently, 26 core targets were identified through analysis, VEGFA and AKT1 were the main candidates. A pathway enrichment analysis showed that overlapping targets were significantly enriched in the PI3K/AKT signaling pathway. A molecular docking analysis revealed tight binding of VEGF to three core compounds, kaempferol, luteolin and quercetin. Experiments showed that WZLYW inhibited mast cell degranulation, regulated VEGFa mRNA and protein expression levels by inhibiting PI3K/AKT and ERK1/2 signaling pathway activation. The mechanism of WZLYW in pruritus may be regulating VEGFa expression. Network pharmacology assays suggested that WLZYW downregulates VEGFa expression by regulating the PI3K/AKT and ERK1/2 signaling pathways in pruritis treatment.

Rapid pruritus reduction with ruxolitinib cream treatment in patients with atopic dermatitis

BACKGROUND

Ruxolitinib cream is a topical formulation of ruxolitinib, a Janus kinase (JAK) 1/JAK2 inhibitor.

OBJECTIVES

To report timing and magnitude of effect of ruxolitinib cream on itch in patients with atopic dermatitis (AD), a highly pruritic inflammatory skin disease.

METHODS

Two phase 3 trials (TRuE-AD1 [NCT03745638]/TRuE-AD2 [NCT03745651]) enrolled patients aged ≥12 years with AD for ≥2 years, Investigator's Global Assessment score of 2 or 3, and 3%-20% affected body surface area. Patients (total N = 1249; median age, 32 years) were randomised (2:2:1) to twice daily 0.75% ruxolitinib cream, 1.5% ruxolitinib cream or vehicle cream for 8 weeks of double-blinded treatment. Worst itch was measured using the numerical rating scale (NRS).

RESULTS

Significantly more patients who applied ruxolitinib cream (either strength) achieved a ≥2-point itch reduction (NRS2) within approximately 12 h versus vehicle (0.75%/1.5% ruxolitinib cream, 16.3%/13.1%; vehicle, 6.9%; both P < 0.05), with further improvements through Week 8 (58.3%/65.1% vs 29.4%; both P < 0.0001). A ≥4-point itch reduction (NRS4) was achieved by significantly more patients who applied 0.75%/1.5% ruxolitinib cream versus vehicle by Day 2 (8.9%/11.2% vs 2.1%; P < 0.005); higher rates were observed at Week 8 (41.5%/51.5% vs 15.8%; P < 0.0001). Median time for the 0.75%/1.5% ruxolitinib cream groups to achieve NRS4 from baseline was 15.0/13.0 days; this endpoint was not reached by the vehicle group.

CONCLUSIONS

Ruxolitinib cream demonstrated rapid improvement in itch in patients with mild to moderate AD that was sustained for 8 weeks. Significantly more patients applying ruxolitinib cream achieved itch NRS2 within approximately 12 h and itch NRS4 by Day 2 versus vehicle.

Early Itch Response with Abrocitinib Is Associated with Later Efficacy Outcomes in Patients with Moderate-to-Severe Atopic Dermatitis: Subgroup Analysis of the Randomized Phase III JADE COMPARE Trial

BACKGROUND

Abrocitinib, an oral Janus kinase 1 inhibitor, provided significant itch relief by week 2 in patients with moderate-to-severe atopic dermatitis (AD) in the phase III JADE COMPARE trial.

OBJECTIVES

This post-hoc analysis of JADE COMPARE aimed to further characterize itch response and determined whether early itch relief could predict subsequent improvements in AD severity.

METHODS

JADE COMPARE was a randomized, double-blind, double-dummy, placebo-controlled trial. Adult patients (aged ≥ 18 years) with moderate-to-severe AD were randomly assigned to receive oral abrocitinib 200 mg or 100 mg once daily, subcutaneous dupilumab 300 mg every other week (after a 600-mg loading dose), or placebo, plus medicated topical therapy for 16 weeks. Assessments were ≥ 4-point improvement in Peak Pruritus Numerical Rating Scale (PP-NRS4) from days 2 to 15, Eczema Area and Severity Index (EASI), Investigator's Global Assessment (IGA) response, and Dermatology Life Quality Index (DLQI) scores at week 12. Association between week 2 PP-NRS4 and efficacy at week 12 was evaluated by chi-squared tests. The predictive value of early response for later efficacy was assessed by area under the receiver operating characteristic curve.

RESULTS

As early as day 4 after treatment, a significantly greater proportion of patients achieved PP-NRS4 response with abrocitinib 200 mg (18.6%) versus dupilumab (5.6%; p < 0.001) and placebo (6.0%; p < 0.003). A similar trend was observed with abrocitinib at the 100-mg dose, with significantly greater PP-NRS4 response rates versus placebo as early as day 9. With both doses of abrocitinib, week 12 IGA 0/1, EASI-75, EASI-90, and DLQI 0/1 response rates were greater in week 2 PP-NRS4 responders than nonresponders; no differences were observed between week 2 PP-NRS4 responders and nonresponders in the dupilumab and placebo groups. Early improvement in PP-NRS at week 2 was associated with skin clearance at week 12 in abrocitinib-treated patients.

CONCLUSIONS

Abrocitinib resulted in rapid relief from itch in patients with moderate-to-severe AD, with significant improvement in itch as early as day 4 after treatment with abrocitinib 200 mg compared with dupilumab and placebo. Abrocitinib-induced itch relief by week 2 was associated with subsequent improvements at week 12. [Video abstract available.] TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03720470. Early itch response with abrocitinib is associated with later efficacy outcomes in patients withmoderate-to-severe atopic dermatitis: subgroup analysis of the randomized phase III JADE COMPARE trial (MP4 335,375kb).

Serum Levels of Eosinophil-Derived Neurotoxin, Platelet-Activating Factor and Vascular Endothelial Growth Factor in Adult Patients with Atopic Dermatitis-A Pilot Study

Atopic dermatitis (AD) is a chronic, highly pruritic, relapsing-remitting inflammatory skin disease. The etiology of AD has not been fully explained yet and complex interactions of various small molecules are still being taken into account. The aim of this research was to investigate the serum eosinophil-derived neurotoxin (EDN), platelet activating factor (PAF) and vascular endothelial growth factor (VEGF) concentrations in relation to the disease severity and pruritus intensity in adult patients with AD. This pilot study was performed on 30 participants (15 patients with AD and 15 healthy controls). Blood samples were taken to examine the serum levels of EDN, PAF and VEGF using the enzyme-linked immunosorbent assay (ELISA) test. The severity of disease was assessed by the Scoring Atopic Dermatitis (SCORAD) index. The intensity of pruritus, as a subjective symptom, was determined by the Visual Analogue Scale (VAS). Obtained results revealed that the EDN (p = 0.016) and VEGF (p = 0.032), but not PAF (p = 0.841) concentrations were significantly higher in patients with AD compared with those of the control group. There was positive correlation between the EDN level and the SCORAD index in patients with AD (r = -0.9, p = 0.037) which was not found for the PAF and VEGF levels. Circulating EDN, PAF and VEGF levels were not significantly correlated with the severity of pruritus. Our results suggest that the END and VEGF serum levels are significantly increased in patients with AD compared to control group. Moreover, EDN might be useful to reflect the severity of symptoms.

Primary cutaneous lymphoma patients seen at a referral dermatological centre in 1 year: A single-centre observational retrospective cohort study of the diagnoses and staging, comorbidities and associated symptoms, treatment performed and clinical course

IMPORTANCE

Primary cutaneous lymphomas (PCL) are rare diseases, but the indolent course makes their prevalence high. Although there are many treatment options, no hierarchy is recommended.

OBJECTIVE

To identify the burden of PCL and describe clinical-pathologic features; associated comorbidities; analyse treatment approaches in real-life and the parameters associated with the achievement of complete response (CR).

DESIGN, SETTING AND PARTICIPANTS

In this study, all the PCL patients (384 patients) consecutively seen at the Dermatologic Clinic of the University of Turin from January 1, 2019 to December 31, 2019, with follow-up updated to December 2020, were included.

MAIN OUTCOMES AND MEASURES

Subtype of PCL, demographic data, time elapsed between first lesions and diagnosis, associated symptoms, comorbidities, staging at diagnosis, high-grade transformation, blood involvement, stage progression, therapies used and response were assessed.

RESULTS

247 were cutaneous T-cell lymphomas (CTCL, 64.3%), 137 cutaneous B-cell lymphomas (CBCL, 35.7%) and the most frequent subtype was MF (48.4%). 62.3% of CTCL patients showed at least one comorbidity, mainly cardiovascular (28.7%), 20.2% show other not cutaneous neoplasms. The main approaches were skin-directed therapies (topical steroids 65.6%; phototherapy 50.2%). 39.3% patients achieved a CR during the disease course. Pruritus, the presence of comorbidities and high-grade transformation were factors associated with failure to achieve CR, whereas stage IA of MF was associated with greater achievement of CR.

CONCLUSIONS AND RELEVANCE

The Th2 cytokine related development of pruritus could justify increased resistance to treatment, while the presence of associated comorbidities could reduce treatment options as well as treatment compliance.

The temperature-sensitive receptors TRPV4 and TRPM8 have important roles in the pruritus of rosacea

BACKGROUND

Certain sensations are the secondary phenotypes of rosacea and affect patients' quality of life. Transient receptor potential (TRP) channels may be involved in its occurrence. However, there is a lack of research independently discussing itch in rosacea.

OBJECTIVES

Our study aimed to investigate risk factors for pruritus in rosacea patients and to discover the molecular mechanism of pruritus.

METHODS

A binary logistic regression model was used to identify significant variables affecting pruritus in 782 rosacea patients. The LL-37 was injected intradermally into the face of mice to establish the animal model. qRT-PCR, immunohistochemistry and immunofluorescence were used to analyse the expression differences in pruritus-related molecules in mouse skin and the corresponding trigeminal ganglion (TG) between pruritus and nonpruritus groups.

RESULTS

The incidence of pruritus in rosacea was 42.46%, and the incidence of other symptoms increased with pruritus. Temperature effects were prominently related to the itch sensation of rosacea. Intradermal injection of LL-37 not only caused rosacea-like facial lesions but also induced a behavioural pattern indicative of pruritus. Increased expression of the temperature-sensitive receptors TRPV4 and TRPM8 was found in pruritic mouse skin and TG and human skin samples.

CONCLUSIONS

In rosacea patients, pruritus occurs frequently along with burning, flushing and sensitivity, most likely due to changes in temperature. The temperature-sensitive receptors TRPV4 and TRPM8 are both involved in the mechanism of pruritus in rosacea.

How Does Botulinum Toxin Inhibit Itch?

Two decades after reports of the anti-pruritic effects of botulinum neurotoxins (BoNTs), there is still no approved product for the anti-itch indication of BoNTs, and most clinical case reports still focus on the off-label use of BoNTs for various itchy conditions. Few randomized clinical trials have been conducted with controversial results, and the beneficial effects of BoNTs against itch are mainly based on case studies and case series. These studies are valuable in presenting the potential application of BoNTs in chronic pruritic conditions, but due to the nature of these studies, they are categorized as providing lower levels of evidence or lower grades of recommendation. To obtain approval for the anti-pruritic indication of BoNTs, higher levels of evidence are required, which can be achieved through conducting large-scale and well-designed studies with proper control groups and established careful and reliable primary and secondary outcomes. In addition to clinical evidence, presenting the mechanism-based antipruritic action of BoNTs can potentially strengthen, accelerate, and facilitate the current efforts towards further investments in accelerating the field towards the potential approval of BoNTs for itchy conditions. This review, therefore, aimed to provide the state-of-the-art mechanisms underlying the anti-itch effect of BoNTs from basic studies that resemble various clinical conditions with itch as a hallmark. Evidence of the neuronal, glial, and immune modulatory actions of BoNTs in reducing the transmission of itch are presented, and future potential directions are outlined.

Generalized resistance to pruritogen-induced scratching in the C3H/HeJ strain

Previously the effect of the pruritogens, such as histamine and chloroquine, was tested in 11 inbred mouse strains, and this study aimed to identify resistant and sensitive strains, consistent with the observation that underlies the large variability in human populations. In the present study, we used the low responder C3H/HeJ (C3H) and the more sensitive C57BL/6J (C57) strain to find out if resistance and sensitivity to develop pruritus is restricted to only histamine and chloroquine or extends to other known pruritogens as well. We tested five additional commonly known pruritogens. We established dose-response relationships by injecting four concentrations of the pruritogens in the range of 0.3, 1, 3, and ten-fold in the nuchal fold. Then we assessed the scratching behavior for 30 min after injection with an automated custom-designed device based on the bilateral implantation of mini-magnets in the hind paws and on single cages placed within a magnetic coil. We found that the resistance to pruritogens is a general phenotype of the C3H strain and extends to all pruritogens tested, including not only histamine and chloroquine, but also endothelin, trypsin, 5-HT (serotonin), the short peptide SLIGRL, and Lysophosphatidic acid (LPA). C57 was more sensitive to all pruritogens and, in contrast to C3H, dose-response relationships were evident for some of the pruritogens. In general, comparable peak scratch responses were observed for the 0.3-fold concentrations of the pruritogens in C57 whereas C3H required at least the ten-fold concentration and still displayed only between 5 and 33% of the scratch responses observed in C57 for the respective pruritogen. The general resistance to pruritogens and the low level of scratching behavior found in the C3H strain is an interesting trait and represents a model for the study of the heritability of itch. It is accompanied in C3H with a higher sensitivity in assays of nociception.

The Efficacy and Safety of Acupuncture in the Treatment of Neurodermatitis: A Systematic Review and Meta-Analysis

Background

Neurodermatitis is a common chronic inflammatory skin disease associated with neurological dysfunction. This study aimed to explore the efficacy and safety of acupuncture and moxibustion in the treatment of neurodermatitis through meta-analysis.

Methods

We comprehensively searched 9 databases, including PubMed, Cochrane Library, EMBASE, Web of Science, Scopus, China National Knowledge Infrastructure (CNKI), Wanfang Database, China Science and Technology Journal Database (VIP), and China Biomedicine (CBM), from their inception to November 15, 2021, for published neurological and clinical randomized controlled trials (RCTs) using acupuncture to treat dermatitis. We also searched gray literature in four databases: Chinese Clinical Trials Registry, Chinese Cochrane Center, Open Grey, and GreyNet International. Two authors independently screened the data, extracted the literature, and evaluated the quality of the literature using Cochrane 5.3.3 and Review Manager 5.4.1 software.

Results

The meta-analysis included 8 studies with a total of 728 participants, including 369 patients in the treatment group and 359 patients in the control group. Compared with conventional treatment, acupuncture significantly increased the effective rate (OR: 2.90, 95% CI: 1.78∼4.75; p < 0.001) and decreased the recurrence rate after treatment (OR: 0.26, 95% CI: 0.12∼0.59; p=0.001). Meanwhile, analysis of disease symptom scores showed that acupuncture group had a greater impact (OR: 3.51, 95% CI: 2.12∼4.91; p < 0.00001). Furthermore, no significant difference in the adverse reaction rate was observed.

Conclusion

Acupuncture is safe and effective in treating neurodermatitis. However, the current level of research evidence is limited, and therefore, larger sample and high-quality RCTs are needed to confirm its safety and effectiveness. Protocol registration number is INPLASY2021110041.

Histamine Is Responsible for the Neuropathic Itch Induced by the Pseudorabies Virus Variant in a Mouse Model

Pseudorabies virus (PRV) is the causative agent of pseudorabies (PR). It can infect a wide range of mammals. PRV infection can cause severe acute neuropathy (the so-called “mad itch”) in nonnatural hosts. PRV can infect the peripheral nervous system (PNS), where it can establish a quiescent, latent infection. The dorsal root ganglion (DRG) contains the cell bodies of the spinal sensory neurons, which can transmit peripheral sensory signals, including itch and somatic pain. Little attention has been paid to the underlying mechanism of the itch caused by PRV in nonnatural hosts. In this study, a mouse model of the itch caused by PRV was elaborated. BALB/c mice were infected intramuscularly with 10⁵ TCID₅₀ of PRV TJ. The frequency of the bite bouts and the durations of itch were recorded and quantified. The results showed that the PRV-infected mice developed spontaneous itch at 32 h postinfection (hpi). The frequency of the bite bouts and the durations of itch were increased over time. The mRNA expression levels of the receptors and the potential cation channels that are relevant to the itch-signal transmission in the DRG neurons were quantified. The mRNA expression levels of tachykinin 1 (TAC1), interleukin 2 (IL-2), IL-31, tryptases, tryptophan hydroxylase 1 (TPH1), and histidine decarboxylase (HDC) were also measured by high-throughput RNA sequencing and real-time reverse transcription PCR. The results showed that the mean mRNA level of the HDC in the DRG neurons isolated from the PRV-infected mice was approximately 25-fold higher than that of the controls at 56 hpi. An immunohistochemistry (IHC) was strongly positive for HDC in the DRG neurons of the PRV-infected mice, which led to the high expression of histamine at the injected sites. The itch of the infected mice was inhibited by chlorphenamine hydrogen maleate (an antagonist for the histamine H1 receptor) in a dose-dependent manner. The mRNA and protein levels of the HDC in the DRG neurons were proportional to the severity of the itch induced by different PRV strains. Taken together, the histamine synthesized by the HDC in the DRG neurons was responsible for the PRV-induced itch in the mice.

Uremic Pruritus: From Diagnosis to Treatment

Uremic pruritus, or chronic kidney disease-associated pruritus, is common, bothersome, and sometimes debilitating in patients with chronic kidney disease or end-stage renal disease. Due to its variable clinical manifestations, the diagnosis of uremic pruritus requires exquisite evaluation. Excluding itch resulting from other dermatological causes as well as other systemic conditions is essential for a proper diagnosis. The pathophysiology of uremic pruritus remains uncertain. Hypotheses including toxin deposition, immune system dysregulation, peripheral neuropathy, and opioid imbalance are supposed. This review summarizes the way to accurately diagnose uremic pruritus and describes the latest treatment options.

Opioidergic Signaling-A Neglected, Yet Potentially Important Player in Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin diseases, the prevalence of which is especially high among children. Although our understanding about its pathogenesis has substantially grown in recent years, and hence, several novel therapeutic targets have been successfully exploited in the management of the disease, we still lack curative treatments for it. Thus, there is an unmet societal demand to identify further details of its pathogenesis to thereby pave the way for novel therapeutic approaches with favorable side effect profiles. It is commonly accepted that dysfunction of the complex cutaneous barrier plays a central role in the development of AD; therefore, the signaling pathways involved in the regulation of this quite complex process are likely to be involved in the pathogenesis of the disease and can provide novel, promising, yet unexplored therapeutic targets. Thus, in the current review, we aim to summarize the available potentially AD-relevant data regarding one such signaling pathway, namely cutaneous opioidergic signaling.

Potential effects of shift work on skin autoimmune diseases

Shift work is associated with systemic chronic inflammation, impaired host and tumor defense and dysregulated immune responses to harmless antigens such as allergens or auto-antigens. Thus, shift workers are at higher risk to develop a systemic autoimmune disease and circadian disruption with sleep impairment seem to be the key underlying mechanisms. Presumably, disturbances of the sleep-wake cycle also drive skin-specific autoimmune diseases, but epidemiological and experimental evidence so far is scarce. This review summarizes the effects of shift work, circadian misalignment, poor sleep, and the effect of potential hormonal mediators such as stress mediators or melatonin on skin barrier functions and on innate and adaptive skin immunity. Human studies as well as animal models were considered. We will also address advantages and potential pitfalls in animal models of shift work, and possible confounders that could drive skin autoimmune diseases in shift workers such as adverse lifestyle habits and psychosocial influences. Finally, we will outline feasible countermeasures that may reduce the risk of systemic and skin autoimmunity in shift workers, as well as treatment options and highlight outstanding questions that should be addressed in future studies.