Over-the-counter topical antipruritic agents are commonly recommended by office-based physicians: an analysis of US practice patterns

Rosmarinic acid ameliorates skin inflammation and pruritus in allergic contact dermatitis by inhibiting mast cell-mediated MRGPRX2/PLCγ1 signaling pathway

BACKGROUND

Allergic contact dermatitis (ACD) is one of the most common dermatoses, which has high disease burden and quality of life impairment. Anti-histamine is not effective in a part of the ACD patients. Thus, the discovery of novel antipruritic therapy is of highly demand.

OBJECTIVE

In this study, we investigated the anti-pruritic effects of rosmarinic acid (RA) and explored the underlying mechanism.

METHOD

SPF Balb/c mice were randomly divided into control group, ACD model group, RA group (1.0 mg/kg) and loratadine (LORA) group (1.5 mg/kg). Back epidermal thickness was recorded. H&E staining was used for pathological observation. Mast cell degranulation was assessed by toluidine blue staining. ELISA assay was employed to detect cytokines levels. Cortistatin-14 (CST-14) and Mas-related G protein-coupled receptor X2 (MRGPRX2) expression was detetcted by RT-PCR and western blot. Molecular docking assay was used to predict the affinity of RA and MRGPRX2. Surface plasmon resonance (SPR) assay was used to verify structure affinity of RA and MRGPRX2.

RESULTS

RA treatment significantly decreased epidermal keratinization and inflammatory cell infiltration in ACD mouse model. Administration of RA significantly reduced secretion of histamine, IL-13, and mRNA expression of CST-14. Furthermore, RA treatment increased mRNA expression of MRGPRX2. In addition, Molecular docking results predict that RA has a good affinity with MRGPRX2. RA displayed a structure affinity (K_D = 8.89 × 10^-4) with MRGPRX2 by SPR. RA inhibited CST-14 and Compound 48/80 (C48/80)-induced mast cell activation via MRGPRX2-PLCγ1-PKC-NF-κB signaling pathway.

CONCLUSION

RA exhibits anti-pruritic and anti-inflammatory effects in ACD mice by inhibiting MRGPRX2-PLCγ1-PKC-NF-κB signaling pathway. RA might emerge as a potential drug for the treatment of pruritus and skin inflammation in the setting of ACD.

A plant-derived TRPV3 inhibitor suppresses pain and itch

BACKGROUND AND PURPOSE

Itching is the most frequent pathology in dermatology that has significant impacts on people's mental health and social life. Transient receptor potential vanilloid 3 (TRPV3) channel is a promising target for treating pruritus. However, few selecetive and potent antagonists have been reported. This study was designed to identify selective TRPV3 antagonist and elucidate its anti-pruritus pharmacology.

EXPERIMENTAL APPROACH

FlexStation and calcium fluorescence imaging were conducted to track the functional compounds. Whole-cell patch clamp was used to record itch-related ion channel currents. Homologous recombination and site-directed mutagenesis were employed to construct TRPV3 channel chimeras and point mutations for exploring pharmacological mechanism. Mouse models were used for in vivo anti-pruritus assay.

KEY RESULTS

An acridone alkaloid (citrusinine-II) was purified and characterized from Atalantia monophylla. It directly interacts with Y564 within S4 helix of TRPV3 to selectively inhibit the channel with a half maximal inhibitory concentration (IC₅₀ ) of 12.43 μM. Citrusinine-II showed potential efficacy to attenuate both chronic and acute itch. Intradermal administration of citrusinine-II (143 ng/skin site) nearly completely inhibited itch behaviours. It also shows significant analgesic effects. Little side effects of the compound are observed.

CONCLUSION AND IMPLICATIONS

By acting as a selective and potent inhibitor of TRPV3 channel, citrusinine-II shows valuable therapeutic effects in pruritus animal models and is a promising candidate drug and/or lead molecule for the development of anti-pruritus drugs.

Anti-pruritic and anti-inflammatory effects of oxymatrine in a mouse model of allergic contact dermatitis

BACKGROUND

Allergic contact dermatitis (ACD) is a highly prevalent inflammatory disease of the skin. As a result of the complex etiology in ACD, therapeutic compounds targeting refractory pruritus in ACD lack efficacy and lead to numerous side effects.

OBJECTIVE

In this study, we investigated the anti-pruritic effects of oxymatrine (OMT) and explored its mechanism of action in a mouse model of ACD.

METHOD

72 male SPF C57BL/6 mice were randomly divided into control group, ACD model group, dexamethasone positive control group (0.08 mg kg-1) and 3 OMT groups (80, 40, 20 mg kg-1). OMT was administrated by intraperitoneal injection 1 h before video recording on day 10, 24 h after 2nd challenge with SADBE. Cheek skin fold thickness was measured before treatment and after recording. H&E staining was used for pathological observation. RT-qPCR, Immunohistochemistry and LEGENDplexTM assay were used to detect cytokines levels. The population of Treg cells in peripheral blood were detected via flow cytometry.

RESULTS

OMT treatment significantly decreases the skin inflammation and scratching bouts. It rescues defects in epidermal keratinization and inflammatory cell infiltration in ACD mice. Administration of OMT significantly reduced levels of IFN-γ, IL-13, IL-17A, TNF-α, IL-22 and mRNA expression of TNF-α and IL-1β. Furthermore, it increased the percentage of Treg cells in peripheral blood of ACD mice.

CONCLUSION

We have demonstrated that OMT exhibits anti-pruritic and anti-inflammatory effects in ACD mice by regulating inflammatory mediators. OMT might emerge as a potential drug for the treatment of pruritus and skin inflammation in the setting of ACD.

A double-blind, randomized clinical study to determine the efficacy of benzocaine 10% on histamine-induced pruritus and UVB-light induced slight sunburn pain

INTRODUCTION

This study aims to explore the efficacy of the topical application of 10% benzocaine for treating pruritus and pain as compared to vehicle ointment.

METHODS

Twenty male subjects were treated in a randomized double-blind fashion with the investigational medicinal product (IMPD) and vehicle. Immediately after the injection of 100 µg histamine on both arms, subjects received topical treatment and pruritus was subsequently assessed with visual analogue scale (VASpruritus) and Eppendorfer questionnaire. Ultraviolet B radiation (UVB) was administered on the back to induce slight sunburn. Twelve hours after UVB application again the IMPD was applied on the right or left upper back and vehicle on the other side and pain related to sunburn was measured with VASpain and pressure algometry.

RESULTS

A trend towards better reduction of pruritus was shown for benzocaine in VASpruritus. For the VASpain significant differences in group comparison (p = 0.02) were observed. Algometer measurements showed onset of pain reduction in the verum group after 20 min whereas in the vehicle-treated area pain relief occurred only after 60 min after application.

CONCLUSIONS

The topically administered ointment containing 10% benzocaine was found superior over vehicle for treating pain, but not pruritus.

Itch as a patient-reported symptom in ambulatory care visits in the United States

BACKGROUND

European studies have shown that itch is a widespread symptom, yet little is known about its frequency in the United States.

OBJECTIVE

We sought to describe ambulatory care visits to clinicians in the United States for which itch was coded as a patient symptom.

METHODS

This study uses retrospective data from the National Ambulatory Medical Care Survey from 1999 through 2009.

RESULTS

Itch was coded as a symptom for an average of 7 million visits per year or approximately 1% of all outpatient visits, which was nearly 40% of the number of visits for the symptom of low back pain. Patients seen in visits for itch were more likely to be black or Asian than other patients (20% vs 14%). They were also more likely than other patients to receive a new medication (68% vs 36%) and were over twice as likely to receive 2 or more new medications (31% vs 14%).

LIMITATIONS

Secondary data sets may not optimally capture patient reports and some of the procedures or medications may have been ordered for reasons other than itch.

CONCLUSION

Visits to clinicians for itch represent a sizeable proportion of ambulatory care visits in the United States, and research on the epidemiology, treatments, and causes of itch should be a priority.

Therapy of pruritus

IMPORTANCE OF THE FIELD

Pruritus is the predominant symptom of skin disease. Owing to the poorly understood pathophysiology, the development of effective treatment modalities for pruritus has proven to be particularly difficult. At present, there is no universally accepted therapy for itch. The purpose of this review is to provide an update on the treatment of pruritus.

AREAS COVERED IN THIS REVIEW

An overview of current, emerging and possible future therapies for pruritus is provided.

WHAT THE READER WILL GAIN

Insights into possible treatment regimes for pruritus in different clinical scenarios.

TAKE HOME MESSAGE

The therapy of pruritus is challenging and at present takes on an individualistic approach. Recent advancements in the mechanisms that underlie this distressing symptom have identified new targets for future therapy.