Antipruritic effects of geraniol on acute and chronic itch via modulating spinal GABA/GRPR signaling.

BACKGROUND AND PURPOSE: Itch (pruritus) is a common unpleasant feeling, often accompanied by the urge of scratching the skin. It is the main symptom of many systemic and skin diseases, which can seriously affect the patient's quality of life. Geraniol (GE; trans-3,7-dimethyl-2,6-octadien-1-ol) is a natural monoterpene with diverse effects, including anti-inflammatory, antioxidant, neuroprotective, anti-nociceptive, and anticancer properties. The study aims to examine the effects of GE on acute and chronic itch, and explore the underlying mechanisms. METHODS: Acute itch was investigated by using Chloroquine and compound 48/80 induced model, followed by manifestation of diphenylcyclopropenone (DCP)-induced allergic contact dermatitis and the acetone-ether-water (AEW)-induced dry skin model in mice. The scratching behavior, skin thickness, c-Fos expression, and GRPR protein expression in the spinal cord were subsequently monitored and evaluated by behavioral tests as well as pharmacological and pharmacogenetic technologies. RESULTS: Dose-dependent intraperitoneal injection of GE alleviated the acute itch, induced by chloroquine and compound 48/80, as well as increased the spinal c-Fos expression. Intrathecal administration of GE suppressed the GABAA receptor inhibitor bicuculline-induced itch, GRP-induced itch, and the GABAergic neuron inhibition-induced itch. Furthermore, the subeffective dose of bicuculline blocked the anti-pruritic effect of GE on the chloroquine and compound 48/80 induced acute itch. GE also attenuated DCP and AEW-induced chronic itch, as well as the increase of spinal GRPR expression in DCP mice. CONCLUSION AND IMPLICATIONS: GE alleviates both acute and chronic itch via modulating the spinal GABA/GRPR signaling in mice. Findings of this study reveal that GE may provide promising therapeutic options for itch management. Also, considering the pivotal role of essential oils in aromatherapy, GE has great application potential in aromatherapy for treating skin diseases, and especially the skin with severe pruritus.

A retrospective multicentric cohort study of checkpoint inhibitors-induced pruritus with focus on management.

BACKGROUND: Limited data on immune checkpoint inhibitor (ICI)-induced pruritus per se and efficacy of different therapeutic modalities in its management exist. OBJECTIVE: To study the quantitative and qualitative characteristics of ICI-induced pruritus per se and to assess the efficacy of the therapeutic modalities usually applied. METHODS: We retrospectively reviewed the records of 91 patients who were under treatment with ICIs for any kind of neoplasia and developed pruritus during treatment. RESULTS: Twenty out of 91 individuals (22.0%) with ICI-induced pruritus had pruritus as the only symptom, while 71/91 (78.0%) presented with pruritus coexisting with an additional cutaneous toxicity. Pruritus was treated with antihistamines (18/20, 90.0%) and/or topical regimens, as first-line choice. In resistant cases, as a second therapeutic intervention, narrow-band UVB (NBUVB), oral steroids and GABA analogs were added (70.0%). Statistical analysis revealed a significant difference in mean pruritus Numerical Rating Scale (NRS) scores between baseline and sequential visits. Moreover, subgroup analysis revealed a significant reduction in mean NRS scores in those treated with phototherapy. LIMITATIONS: Retrospective design, low number of patients and survivorship bias. CONCLUSION: Pruritus per se was present in a substantial portion of our cohort (22.0%). Our study confirms the efficacy of current treatment strategies and suggests NBUVB as a potential steroid-sparing therapeutic alternative.

Topical borneol relieves nonhistaminergic pruritus via targeting TRPA1 and TRPM8 channels in peripheral nerve terminals of mice.

Borneol has been used successfully for the treatment of itchy skin in traditional Chinese medicine. However, the antipruritic effect of borneol has rarely been studied, and the mechanism is unclear. Here, we showed that topical application of borneol on skin substantially suppressed pruritogen chloroquine- and compound 48/80-induced itching in mice. The potential targets of borneol, including transient receptor potential cation channel subfamily V member 3 (TRPV3), transient receptor potential cation channel subfamily A member 1 (TRPA1), transient receptor potential cation channel subfamily M member 8 (TRPM8), and gamma-aminobutyric acid type A (GABAA) receptor were pharmacologically inhibited or genetically knocked out one by one in mouse. Itching behavior studies demonstrated that the antipruritic effect of borneol is largely independent of TRPV3 and GABAA receptor, and TRPA1 and TRPM8 channels are responsible for a major portion of the effect of borneol on chloroquine-induced nonhistaminergic itching. Borneol activates TRPM8 and inhibits TRPA1 in sensory neurons of mice. Topical co-application of TRPA1 antagonist and TRPM8 agonist mimicked the effect of borneol on chloroquine-induced itching. Intrathecal injection of a group II metabotropic glutamate receptor antagonist partially attenuated the effect of borneol and completely abolished the effect of TRPM8 agonist on chloroquine-induced itching, suggesting that a spinal glutamatergic mechanism is involved. In contrast, the effect of borneol on compound 48/80-induced histaminergic itching occurs through TRPA1-and TRPM8-independent mechanisms. Our work demonstrates that borneol is an effective topical itch reliever, and TRPA1 inhibition and TRPM8 activation in peripheral nerve terminals account for its antipruritic effect.

Dictamnine ameliorates chronic itch in DNFB-induced atopic dermatitis mice via inhibiting MrgprA3.

Chronic itch is the most prominent feature of atopic dermatitis (AD), and antihistamine treatment is often less effective in reducing clinical pruritus severity in AD. Multiple studies have shown that histamine-independent itch pathway is thought to predominate in AD-induced chronic itch. Mas-related G-protein-coupled receptor (Mrgpr) A3+ sensory neurons have been identified as one of the major itch-sensing neuron populations, and transient receptor potential (TRP) channel A1 is the key downstream of MrgprA3-mediated histamine-independent itch. MrgprA3-TRPA1 signal pathway is necessary for the development of chronic itch and may be the potentially promising target of chronic itch in AD. Dictamnine is one of the main quinoline alkaloid components of Cortex Dictamni (a traditional Chinese medicine widely used in clinical treatment of skin diseases). However, the anti-inflammatory and anti-pruritic effect of dictamnine on AD have not been reported. In this study, we used the 2,4-dinitrofluorobenzene (DNFB)-induced AD mouse model to observe the scratching behavior, inflammatory manifestations, and to detect the expression of MrgprA3 and TRPA1 in skin and DRG. The data demonstrated that dictamnine effectively inhibited AD-induced chronic itch, inflammation symptoms, epidermal thickening, inflammatory cell infiltration, and downregulated the expression of MrgprA3 and TRPA1. Furthermore, dictamnine restrained the excitability of MrgprA3+ and TRPA1+ neurons. Molecular docking also indicated that dictamnine has better binding affinity with MrgprA3. These results suggest that dictamnine may inhibit chronic itch caused by AD through the MrgprA3-TRPA1 mediated histamine-independent itch pathway, and may have a potential utility in AD treatment.

miRNA-203b-3p Induces Acute and Chronic Pruritus through 5-HTR2B and TRPV4.

Growing evidence indicates that transient receptor potential (TRP) channels contribute to different forms of pruritus. However, the endogenous mediators that cause itch through transient receptor potential channels signaling are poorly understood. In this study, we show that genetic deletion or pharmacological antagonism of TRPV4 attenuated itch in a mouse model of psoriasis induced by topical application of imiquimod. Human psoriatic lesions showed increased expression of several microRNAs, including the miR-203b-3p, which induced a calcium ion response in rodent dorsal root ganglion neurons and scratching behavior in mice through 5-HTR2B activation and the protein kinase C‒dependent phosphorylation of TRPV4. Computer simulation revealed that the miR-203b-3p core sequence (GUUAAGAA) that causes 5-HTR2B/TRPV4-dependent itch targets the extracellular side of 5-HTR2B by interacting with a portion of the receptor pocket consistent with its activation. Overall, we reveal the unconventional pathophysiological role of an extracellular microRNA that can behave as an itch promoter through 5-HTR2B and TRPV4.

Acupuncture and osteopathic medicine for atopic dermatitis: a three-armed, randomized controlled explorative clinical trial.

BACKGROUND: Patients with atopic dermatitis (AD) frequently use acupuncture (ACU) and osteopathic medicine (OM), although their therapeutic benefits are unclear. AIM: To investigate the effectiveness of ACU and OM in patients with AD. METHODS: In a three-armed, single-centre, randomized controlled open explorative clinical trial, adult patients with AD received ACU, OM or no study intervention (control group; CG) plus routine care. Outcomes included disease severity (SCORing Atopic Dermatitis; SCORAD), itching intensity (visual analogue scale; VAS), frequency of topical corticosteroid (TCS) use over 7 days and cost-effectiveness. Endpoints were analysed by analysis of covariance adjusted for the respective baseline value and TCS use. RESULTS: Overall, 121 patients (92 women, 29 men) with a mean ± SD age of 31.4 ± 10.5 years were randomized. After 12 weeks, the adjusted means (95% CI) for ACU, OM and control were, respectively, 22.3 (18.3-26.3), 26.4 (22.6-30.2) and 23.7 (19.9-27.5) for SCORAD (P = 0.32); 27.9 (19.5-36.4), 35.0 (26.9-43.0) and 42.3 (34.7-50.0) for VAS itching (P < 0.05); and 2.3 (0.8-3.9), 1.9 (0.4-3.5) and 4.3 (2.6-6.0), for TCS use (P = 0.10). ACU and OM were not cost-effective compared with the CG. CONCLUSION: Although no differences in disease severity were found, our findings indicate that ACU might reduce itching in patients with AD. Furthermore, ACU and OM showed a trend towards reducing TCS use.

Hypothalamic response with PKA/CREB signaling is associated with direct cerebroventricular administration of bombesin-induced scratching.

Bombesin (BN) is an itch-specific mediator that causes intense itch-scratching activity in mammals. Although most examinations of BN-induced itch processing have focused on the spinal cord, the involvement of central nervous system mechanisms remains unclear. Here, we investigated how relationships among hypothalamic regions regulate BN-mediated itch-scratch processes. We found that intracerebroventricular (i.c.v.) administration of BN (0.04-4 µg) elicited intense itch scratching in mice, whereas BN (0.4-400 µg) administered via intravenous tail injection failed to evoke a scratching response. Additionally, nalfurafine had no significant effects on BN-induced scratching behavior, indicating that central modulation of BN is distinct from histamine-mediated histaminergic itch and chloroquine-mediated non-histaminergic itch signaling pathways. We labeled BN with a fluorescent tag, 7-nitrobenz-2-oxa-1 (NBD), and traced its fluorescence in the hypothalamus for 30 min following i.c.v. NBD-BN administration. Accordingly, we confirmed that i.c.v. administration of BN enhanced c-Fos expression in the dorsal medial nucleus of the hypothalamus, where neuromedin B receptors and gastrin-releasing peptide receptors are highly expressed. Interestingly, in situ injection of BN into the hypothalamus immediately and robustly induced itch-scratching behavior. Moreover, gene transcripts and western blot assay revealed that BN receptor-dependent PKA/CREB signaling was upregulated in the hypothalamus after i.c.v. administration of BN. Consistently, pretreatment with a PKA inhibitor, Rp-cAMP, significantly reduced BN-induced scratching behavior. Our results indicate that the dorsal medial nucleus of the hypothalamus may be a key nucleus in mediating BN-mediated itch and hypothalamic PKA/CREB signaling is involved in regulating BN-mediated itch.

A Randomized Clinical Trial on Therapeutic Effects of Myrtus communis L. Cream on Chronic Skin Lesions and Quality of Life of Sulfur Mustard-exposed Veterans

Abstract: Sulfur mustard is one of the chemical warfare agent. It rapidly reacts with the cutaneous tissues and other tissues, leading to various devastating long-term effects on human health. Mustard-exposed veterans suffer from its chronic skin problems, including itching, burning sensation, and eczema. We aimed to evaluate the protective effects of Myrtus communis L. (myrtle) on chronic skin lesions and quality of life of sulfur mustard-exposed veterans. In this randomized, double-blind clinical trial, 60 sulfur mustard-exposed patients were evaluated. Thirty patients received myrtle essence 5% cream (case group) and 30 patients received Eucerin cream (placebo group) twice in a day for one month. Then, We assessed the chronic skin problems and itching-related parameters (such as the itching time, severity, distribution, frequency, and calculated itching score), duration of sleep, number of waking up at night, and quality of life in the both groups. Our analysis of data revealed that application of myrtle cream effectively decreased skin problems including; itching and burning sensation. Additionally, myrtle markedly decreased skin lesion symptoms such as excoriation in the case group as compared with before treatment. Noticeably, myrtle cream significantly improved quality of life of the patients in the case group. The present study provides more in-depth information regarding the protective role of myrtle on the sulfur mustard-induces skin complication. Also, myrtle effectively improved quality of life of the sulfur mustard-exposed veterans.

Oxymatrine screened from Sophora flavescens by cell membrane immobilized chromatography relieves histamine-independent itch.

OBJECTIVES: This study aimed to discover the active compounds of Sophora flavescens Ait. (SF), the anti-itch effects and underlying mechanisms of oxymatrine (OMT), one of the bioactive compounds from SF. METHODS: Dorsal root ganglion cell membrane immobilized chromatography was used to screen potential anti-pruritic active compounds from SF. The scratching behaviour was analysed to systematically study the anti-pruritic effects of OMT in chloroquine- (CQ), peptide Ser-Leu-Ile-Gly-Arg-Leu- (SLIGRL), histamine- (HIS) and allyl-isothiocyanate-(AITC)-induced itch mice models. Real-time quantitative PCR, in-vivo study and molecular docking were employed to explore the underlying mechanisms. KEY FINDINGS: All in all, 21 compounds of SF were identified and 5 potential bioactive compounds were discovered. OMT significantly reduced scratching bouts in two HIS-independent itch models induced by CQ and SLIGRL but was not effective in the HIS-induced itch model. OMT reduced scratching bouts in a dose-dependent manner and decreased the messenger RNA (mRNA) expression of transient receptor potential ankyrin 1 (TRPA1) channel in two HIS-independent itch models; in addition, OMT reduced the wipes and scratching bouts induced by AITC. CONCLUSIONS: This study discovered five potential anti-pruritic compounds including OMT in the SF extract, and OMT has strong anti-pruritic effects in HIS-independent itch via TRPA1 channel.

Acupuncture ameliorates not only atopic dermatitis-like skin inflammation but also acute and chronic serotonergic itch possibly through blockade of 5-HT2 and 5-HT7 receptors in mice.

Acupuncture has been known to be effective for atopic dermatitis, especially ameliorating itch; however, its mechanisms are still unclear. The aim of this study was to test the anti-itch effects of acupuncture and to investigate its possible mechanisms. Acupuncture was performed at Gok-Ji (LI11) acupoints just before the injection of pruritogens in the mouse cheek model of acute itch and of MC903-induced atopic dermatitis displaying serotonergic chronic itch. Acupuncture significantly reduced acute itch triggered by compound 48/80, chloroquine, or especially serotonin. It also markedly reduced scratching behaviors evoked by the serotonin 5-HT2 receptor agonist α-methylserotonin and selective 5-HT7 receptor agonist LP 44. In addition, acupuncture treatment at LI11 had the preventive and therapeutic effects on persistent itch as well as the robust skin inflammation with epidermal thickening in mice with MC903-induced atopic dermatitis. It also considerably reduced the increased expression of 5-HT2A, 5-HT2B and 5-HT7 receptors in atopic dermatitis-like skin lesions in mice treated with MC903. Taken together, these findings highlight that acupuncture significantly ameliorates not only skin inflammation, but also acute and chronic serotonergic itch, possibly through blockade of serotonin 5-HT2 and 5-HT7 receptors.

Nocebo Effects on Cowhage-evoked Itch: A Randomized Controlled Trial of Classical Conditioning and Observational Learning.

To investigate learning processes underlying nocebo effects on itch, this study measured the efficacy of classical conditioning and observational learning for inducing nocebo effects on cowhage-evoked itch and scratching behaviour. A total of 58 healthy female participants were assigned to classical conditioning, observational learning, or sham conditioning groups. In the classical conditioning group, experimenters associated the application of an inert gel with increased itch intensity themselves. In the observational learning group, a video of the conditioning paradigm was shown. Nocebo effects were measured as the difference in itch or scratching between control and nocebo test phase trials, compared between learning and control groups. Compared with sham conditioning, classical conditioning induced a significant nocebo effect on itch, while observational learning did not. No nocebo effect on scratching was detected. These results highlight the role that learning through direct experiences plays in pruritic symptoms. Future research should investigate how a patient's history of unsuccessful treatments shapes treatment outcomes.

Eosinophils adhesion assay as a tool for phenotypic drug screening - The pharmacology of 1,3,5 - Triazine and 1H-indole like derivatives against the human histamine H4 receptor.

Histamine is a pleiotropic biogenic amine, having affinity towards four distinct histamine receptors. The existing pharmacological studies suggest the usefulness of histamine H4 receptor ligands in the treatment of many inflammatory and immunomodulatory diseases, including allergic rhinitis, asthma, atopic dermatitis, colitis or pruritus. Up to date, several potent histamine H4 receptor ligands were developed, none of which was registered as a drug yet. In this study, a series of potent indole-like and triazine derivatives were tested, in radioligand displacement and functional assays at histamine H4 receptor, as well as in human eosinophils adhesion assay to endothelium. For selected compounds permeability, cytotoxicity, metabolic and in vivo studies were conducted. Adhesion assay differentiated the activity of different groups of compounds with a known affinity towards the histamine H4 receptor. Most of the tested compounds downregulated the number of adherent cells. However, adhesion assay revealed additional properties of tested compounds that had not been detected in radioligand displacement and aequorin-based functional assays. Furthermore, for some tested compounds, these abnormal effects were confirmed during the in vivo studies. In conclusion, eosinophils adhesion assay uncovered pharmacological activity of histamine H4 receptor ligands that has been later confirmed in vivo, underscoring the value of well-suited cell-based phenotypic screening approach in drug discovery.

Resolvin D3 controls mouse and human TRPV1-positive neurons and preclinical progression of psoriasis.

Rationale: Psoriasis is a chronic inflammatory disease caused by a complex interplay between the immune and nervous systems with recurrent scaly skin plaques, thickened stratum corneum, infiltration and activation of inflammatory cells, and itch. Despite an increasing availability of immune therapies, they often have adverse effects, high costs, and dissociated effects on inflammation and itch. Activation of sensory neurons innervating the skin and TRPV1 (transient receptor potential vanilloid 1) are emerging as critical components in the pathogenesis of psoriasis, but little is known about their endogenous inhibitors. Recent studies have demonstrated that resolvins, endogenous lipid mediators derived from omega-3 fatty acids, are potent inhibitors of TRP channels and may offer new therapies for psoriasis without known adverse effects. Methods: We used behavioral, electrophysiological and biochemical approaches to investigate the therapeutic effects of resolvin D3 (RvD3), a novel family member of resolvins, in a preclinical model of psoriasis consisting of repeated topical applications of imiquimod (IMQ) to murine skin, which provokes inflammatory lesions that resemble human psoriasis. Results: We report that RvD3 specifically reduced TRPV1-dependent acute pain and itch in mice. Mechanistically, RvD3 inhibited capsaicin-induced TRPV1 currents in dissociated dorsal root ganglion (DRG) neurons via the N-formyl peptide receptor 2 (i.e. ALX/FPR2), a G-protein coupled receptor. Single systemic administration of RvD3 (2.8 mg/kg) reversed itch after IMQ, and repeated administration largely prevented the development of both psoriasiform itch and skin inflammation with concomitant decreased in calcitonin gene-related peptide (CGRP) expression in DRG neurons. Accordingly, specific knockdown of CGRP in DRG was sufficient to prevent both psoriasiform itch and skin inflammation similar to the effects following RvD3 administration. Finally, we elevated the translational potential of this study by showing that RvD3 significantly inhibited capsaicin-induced TRPV1 activity and CGRP release in human DRG neurons. Conclusions: Our findings demonstrate a novel role for RvD3 in regulating TRPV1/CGRP in mouse and human DRG neurons and identify RvD3 and its neuronal pathways as novel therapeutic targets to treat psoriasis.

Application of Zizao Yangrong Granules for Treating Targeted Drugs-Related Skin Xerosis: A Randomized Double-Blinded Controlled Study.

Background: Dermatologic toxicities are the most common side effects associated with the targeted drugs epidermal growth factor receptor inhibitors (EGFRIs), in which xerosis commonly complicated by pruritus severely disturbs the quality of life. The study has observed the curative effect of Zizao Yangrong granules (ZYG) from Chishui Xuanzhu in the treatment of EGFRIs-related xerosis and pruritus, as well as evaluating the safety of the prescription. Methods: Patients (n = 68) who had xerosis after using EGFRIs were enrolled and then randomly divided into the treatment group and control group, respectively, receiving ZYG and placebo granules combined with vitamin E ointment. The intervention lasted 4 weeks. Changes in xerosis and pruritus were observed, and blood routine examination as well as liver and kidney function are observed as safety indexes. The water content of skin and qualify of life were observed. Results: A total of 66 out of 68 patients finished the study with 34 patients in each group. The effective rates of xerosis among the treatment group and control group were 84.8% and 69.7% after 2 weeks' treatment (P < .05), while they were 84.8% and 75.8% after 4 weeks' treatment (P < .05). The patients in the experimental group had better quality of life than that in the control group (P = .045). Conclusion: ZYG can effectively improve the skin dryness associated with EGFRIs, and significantly improve the quality of life of patients with good safety; however, larger randomized controlled trials are needed to verify these findings.

Formulation and clinical evaluation of the standardized Litchi chinensis extract for skin hyperpigmentation and aging treatments.

INTRODUCTION: The standardized litchi extract had been revealed on phytochemical actives, in vitro and cellular activities against aging and darkening of skin. However, a formulation containing the extract has never been developed as per clinical evaluated. MATERIALS AND METHODS: The litchi serum was developed, safety and efficacy were clinically evaluated in human volunteers. The stable and none irritated 0.05 and 0.1% litchi serums were randomized-single blind placebo control clinical applied on the inner forearm of 29 volunteers for a consecutive 112 days and monitored by Mexameter® MX18, Cutometer® MPA 580 and Visioscan® VC 98. RESULTS: Skin lightening efficacy of the 0.1% and 0.05% litchi serum was significantly (P<0.001 and P<0.05) higher than the placebo. Skin elasticity and wrinkle reduction was significantly (P<0.05 and P<0.005) achieved by the 0.1% litchi serum. The efficacy of litchi serums was confirmed by a split-face, randomized, single-blind controlled that the 0.1% litchi serum was significantly (P<0.05) better than the 0.05% one of all examined parameters. CONCLUSION: Safety and efficacy of litchi extract are clinically confirmed for hyperpigmentation and aging of skin treatments.

Complementary roles of murine NaV1.7, NaV1.8 and NaV1.9 in acute itch signalling.

Acute pruritus occurs in various disorders. Despite severe repercussions on quality of life treatment options remain limited. Voltage-gated sodium channels (NaV) are indispensable for transformation and propagation of sensory signals implicating them as drug targets. Here, NaV1.7, 1.8 and 1.9 were compared for their contribution to itch by analysing NaV-specific knockout mice. Acute pruritus was induced by a comprehensive panel of pruritogens (C48/80, endothelin, 5-HT, chloroquine, histamine, lysophosphatidic acid, trypsin, SLIGRL, ß-alanine, BAM8-22), and scratching was assessed using a magnet-based recording technology. We report an unexpected stimulus-dependent diversity in NaV channel-mediated itch signalling. NaV1.7-/- showed substantial scratch reduction mainly towards strong pruritogens. NaV1.8-/- impaired histamine and 5-HT-induced scratching while NaV1.9 was involved in itch signalling towards 5-HT, C48/80 and SLIGRL. Furthermore, similar microfluorimetric calcium responses of sensory neurons and expression of itch-related TRP channels suggest no change in sensory transduction but in action potential transformation and conduction. The cumulative sum of scratching over all pruritogens confirmed a leading role of NaV1.7 and indicated an overall contribution of NaV1.9. Beside the proposed general role of NaV1.7 and 1.9 in itch signalling, scrutiny of time courses suggested NaV1.8 to sustain prolonged itching. Therefore, NaV1.7 and 1.9 may represent targets in pruritus therapy.