The excimer lamp induces cutaneous nerve degeneration and reduces scratching in a dry-skin mouse model

Excimer light effect on neurogenic inflammation in active versus stable psoriasis lesions

Neurogenic inflammation, mediated by T helper 17 cell (Th17) and neurons that release neuropeptides such as substance P (SP), is thought to play a role in the pathogenesis of psoriasis. Excimer light is used in the treatment of psoriasis via induction of T cell apoptosis. The objective of this study is to study the effect of excimer light on active versus stable psoriasis and investigate the levels of substance P and its receptor in both groups. The study included 27 stable and 27 active psoriatic patients as well as 10 matched healthy controls. Clinical examination (in the form of local psoriasis severity index (PSI) and visual analogue scale (VAS)) was done to determine disease severity, level of itching, and quality of life. Tissue levels of SP and neurokinin-1 receptor (NK-1R) were measured by ELISA before and after 9 excimer light sessions in 43 patients. A statistically significant lower levels of PSI and VAS were reached after therapy with no significant difference between the stable and active groups. The mean tissue levels of SP before therapy were significantly higher than the control group. Lower levels of SP and NK-1 receptor were found after treatment overall and in each group. Excimer therapy can be effective for both stable and active plaque psoriasis and this effect could be partly through its role on ameliorating the neurogenic inflammation.

Treatment Options for Troublesome Itch

Itch (or pruritus) is an unpleasant sensation, inducing the desire to scratch. It is also a major and distressing symptom of many skin and systemic diseases. The involvement of histamine, which is a major itch mediator, has been extensively examined. Recent studies suggest that histamine-independent pathways may play roles in chronic itch. Therefore, antihistamines are not always effective in the treatment of patients with chronic itch. The development of biologics and κ-opioid receptor (KOR) agonists has contributed to advances in the treatment of itch; however, since biologics are expensive for patients to purchase, some patients may limit or discontinue their use of these agents. Furthermore, KOR agonists need to be prescribed with caution due to risks of side effects in the central nervous system. Janus kinase (JAK) inhibitors are sometimes associated with side effects, such as infection. In this review, we summarize antidepressants, antineuralgics, cyclosporine A, antibiotics, crotamiton, phosphodiesterase 4 inhibitor, botulinum toxin type A, herbal medicines, phototherapy, and acupuncture therapy as itch treatment options other than antihistamines, biologics, opioids, and JAK inhibitors; we also explain their underlying mechanisms of action.

Peripheral itch sensitization in atopic dermatitis

Atopic dermatitis is a skin disorder caused by skin dryness and barrier dysfunction, resulting in skin inflammation and chronic itch (or pruritus). The pathogenesis of atopic dermatitis is thought to be initiated by a lowering of the itch threshold due to dry skin. This lowering of the itch threshold is at least partially due to the increase in intraepidermal nerve fibers and sensitization of sensory nerves by interleukin (IL)-33 produced and secreted by keratinocytes. Such skin is easily prone to itch due to mechanical stimuli, such as rubbing of clothing and chemical stimuli from itch mediators. In patients with atopic dermatitis, once itch occurs, further itch is induced by scratching, and the associated scratching breaks down the skin barrier. Disruption of the skin barrier allows entry into the epidermis of external foreign substances, such as allergens derived from house dust mites, leading to an increased induction of type 2 inflammatory responses. As a result, type 2 cytokines IL-4, IL-13, and IL-31 are mainly secreted by Th2 cells, and their action on sensory nerve fibers causes further itch sensitization. These sequences of events are thought to occur simultaneously in patients with atopic dermatitis, leading to a vicious itch-scratch cycle. This vicious cycle becomes a negative spiral that leads to disease burden. Therefore, controlling itch is essential for the treatment of atopic dermatitis. In this review, we summarize and discuss advances in the mechanisms of peripheral itch sensitization in atopic dermatitis, focusing on skin barrier-neuro-immune triadic connectivity.

Efficacy of Phototherapy With 308-nm Excimer Light for Skin Microbiome Dysbiosis and Skin Barrier Dysfunction in Canine Atopic Dermatitis

The management of canine atopic dermatitis, an allergic skin disorder, is challenging. To investigate the effect of phototherapy using a 308-nm excimer light as a topical treatment for canine atopic dermatitis, 10 dogs with canine atopic dermatitis and 10 with non-allergic skin were enrolled in this study. Phototherapy was applied every 7 days for a total of 2 months. The skin microbiome, skin barrier function, and clinical outcomes were evaluated after phototherapy. Phototherapy significantly changed the composition of the skin microbiome of dogs with atopic dermatitis and significantly increased the relative abundance of the phyla Actinobacteria and Cyanobacteria. It significantly alleviated the clinical signs of canine atopic dermatitis without serious adverse effects. Transepidermal water loss, as a measure of skin barrier function, significantly decreased after phototherapy. In addition, phototherapy increased microbial diversity and decreased the relative abundance of Staphylococcus pseudintermedius associated with the severity of canine atopic dermatitis. These results suggest that the excimer light therapy is a suitable and safe therapeutic option for canine atopic dermatitis, which is also a spontaneous animal model of atopic dermatitis.

A Novel In Vitro Assay Using Human iPSC-Derived Sensory Neurons to Evaluate the Effects of External Chemicals on Neuronal Morphology: Possible Implications in the Prediction of Abnormal Skin Sensation

Neuronal morphological changes in the epidermis are considered to be one of causes of abnormal skin sensations in dry skin-based skin diseases. The present study aimed to develop an in vitro model optimised for human skin to test the external factors that lead to its exacerbation. Human-induced pluripotent stem cell-derived sensory neurons (hiPSC-SNs) were used as a model of human sensory neurons. The effects of chemical substances on these neurons were evaluated by observing the elongation of nerve fibers, incidence of blebs (bead-like swellings), and the expression of nicotinamide mononucleotide adenylyl transferase 2 (NMNAT2). The nerve fiber length increased upon exposure to two common cosmetic preservatives-methylparaben and phenoxyethanol-but not to benzo[a]pyrene, an air pollutant at the estimated concentrations in the epidermis. Furthermore, the incidence of blebs increased upon exposure to benzo[a]pyrene. However, there was a decrease in the expression of NMNAT2 in nerve fibers, suggesting degenerative changes. No such degeneration was found after methylparaben or phenoxyethanol at the estimated concentrations in the epidermis. These findings suggest that methylparaben and phenoxyethanol promote nerve elongation in hiPSC-SNs, whereas benzo[a]pyrene induces nerve degeneration. Such alterations may be at least partly involved in the onset and progression of sensitive skin.

2020 guidelines for the diagnosis and treatment of prurigo

Prurigo is a treatment-resistant skin disease characterized by multiple isolated papules/nodules that cause severe itch. Prurigo papules/nodules occur either as primary lesions or as secondary lesions due to persistent scratching. The fundamental concepts and classifications of prurigo have not been sufficiently established, and considerable confusion remains regarding this topic. Clinical guidelines for chronic prurigo in Japan were published in 2012 in an attempt to reduce confusion regarding the concepts of prurigo and to standardize laboratory tests and treatments. However, the diagnostic terms for prurigo and associated concepts have changed over time, and new forms of treatment are under development. We have, thus, updated and revised the guidelines to classify prurigo based on clinical forms and causes, and disease name classifications based on the clinical form have been further simplified, such as prurigo nodularis, prurigo chronica multiformis, and prurigo (not otherwise specified). Expressions for acute, subacute, and chronic forms are not used. These guidelines outline the current concepts and specify treatments for prurigo.

2020 guidelines for the diagnosis and treatment of cutaneous pruritus

The mechanisms underlying itch are not fully understood. Physicians usually encounter difficulty controlling itch in generalized pruritus. Since only a small percentage of patients with generalized pruritus respond to antihistamines (H₁ receptor antagonists), a variety of itch mediators and mechanisms other than histaminergic signals are considered to be involved in itch for these non-responsive patients. In 2012, we created guidelines for generalized pruritus. Those guidelines have been updated and revised to make some of the definitions, diagnostic terms, and classifications more applicable to daily clinical practice. Cutaneous pruritus as designated in these guidelines is a disease characterized by itch without an observable rash. Generalized pruritus (without skin inflammation) is defined as the presence of itch over a wide area, and not localized to a specific part of the body. This entity includes idiopathic pruritus, pruritus in the elderly, symptomatic pruritus, pregnancy-associated pruritus, drug-induced pruritus, and psychogenic pruritus. Localized pruritus (without skin inflammation) represents fixed itch localized to a specific part of the body, and includes anogenital pruritus, scalp pruritus, notalgia paresthetica, and brachioradial pruritus. These guidelines outline the current concepts and specify the diagnostic methods/treatments for cutaneous pruritus.

308-nm Excimer Lamp vs. Combination of 308-nm Excimer Lamp and 10% Liquor Carbonis Detergens in Patients With Scalp Psoriasis: A Randomized, Single-Blinded, Controlled Trial

Background: Scalp psoriasis is usually refractory to treatment. Excimer devices have been proved to be a promising therapeutic option in psoriasis. Greater efficacy of phototherapy can be achieved by concurrent use of coal tar derivatives.

Objective: We aimed to compare efficacy and safety between 308-nm excimer lamp monotherapy and a combination of 308-nm excimer lamp and 10% liquor carbonis detergens in the treatment of scalp psoriasis.

Methods: In this randomized, evaluator-blinded, prospective, comparative study, 30 patients with scalp psoriasis received either 308-nm excimer lamp monotherapy or a combination of 308-nm excimer lamp and 10% liquor carbonis detergens twice per week until complete remission of the scalp or for a total of 30 sessions. Efficacy was evaluated by the improvement of Psoriasis Scalp Severity Index (PSSI) score, itch score, and Scalpdex score.

Results: Both treatments induced significant improvement in PSSI score with greater reduction observed in the combination group. At 30th visit, a 75% reduction in PSSI (PSSI75) was attained by 4 (28.6%) and 9 (69.2%) patients treated with monotherapy and combination therapy, respectively (P < 0.05).

Conclusions: Excimer lamp is well-tolerated in patients with scalp psoriasis and liquor carbonis detergens can be used as a combination therapy to improve the efficacy of excimer lamp.

Intractable Itch in Atopic Dermatitis: Causes and Treatments

Itch or pruritus is the hallmark of atopic dermatitis and is defined as an unpleasant sensation that evokes the desire to scratch. It is also believed that itch is a signal of danger from various environmental factors or physiological abnormalities. Because histamine is a well-known substance inducing itch, H₁-antihistamines are the most frequently used drugs to treat pruritus. However, H₁-antihistamines are not fully effective against intractable itch in patients with atopic dermatitis. Given that intractable itch is a clinical problem that markedly decreases quality of life, its treatment in atopic dermatitis is of high importance. Histamine-independent itch may be elicited by various pruritogens, including proteases, cytokines, neuropeptides, lipids, and opioids, and their cognate receptors, such as protease-activated receptors, cytokine receptors, Mas-related G protein-coupled receptors, opioid receptors, and transient receptor potential channels. In addition, cutaneous hyperinnervation is partly involved in itch sensitization in the periphery. It is believed that dry skin is a key feature of intractable itch in atopic dermatitis. Treatment of the underlying conditions that cause itch is necessary to improve the quality of life of patients with atopic dermatitis. This review describes current insights into the pathophysiology of itch and its treatment in atopic dermatitis.

Current treatments for atopic dermatitis in Japan

The goal of a treatment regimen for atopic dermatitis is to reach and maintain a state where the patient exhibits mild symptoms or an absence of symptoms, and the patient should not experience disturbance during daily activities. The basis of a treatment regimen for atopic dermatitis is topical therapy, and currently there exist topical corticosteroids, tacrolimus and delgocitinib. Using these, proactive therapy is performed as maintenance therapy after remission induction therapy. However, in cases of moderate to severe atopic dermatitis, topical drugs alone cannot induce remission and systemic therapies such as cyclosporin, ultraviolet therapy, and dupilumab should be used in combination. In particular, dupilumab has many advantages such as high efficacy, relatively few adverse reactions, and ease of use in elderly patients with severe atopic dermatitis. In this review, we present a treatment algorithm for atopic dermatitis that emphasizes the importance of maintaining remission after induction of remission, and summarizes the characteristics of current medication therapy for atopic dermatitis in Japan.

Social defeat stress exacerbates atopic dermatitis through downregulation of DNA methyltransferase 1 and upregulation of C-C motif chemokine receptor 7 in skin dendritic cells

DNA methylation is an epigenetic modification that regulates gene transcription. DNA methyltransferase 1 (DNMT1) plays an important role in DNA methylation. However, the involvement of DNMT1 and DNA methylation in the pathogenesis of atopic dermatitis (AD) remains unclear. In this study, microarray analysis revealed that peripheral blood mononuclear cells of AD patients with low DNMT1 expression (DNMT1-low) highly expressed dendritic cell (DC) activation-related genes. Also, DNMT1-low AD patients exhibited a higher itch score compared to AD patients with high DNMT1 expression (DNMT1-high). By using an AD-like mouse model induced by the application of Dermatophagoides farinae body ointment, we found that Dnmt1 expression was decreased, while the expression of C-C chemokine receptor type 7 (Ccr7) was upregulated in mouse skin DCs. Furthermore, mice exposed to social defeat stress exhibited Dnmt1 downregulation and Ccr7 upregulation in skin DCs. Additionally, dermatitis and itch-related scratching behavior were exacerbated in AD mice exposed to stress. The relationship between low DNMT1 and itch induction was found in both human AD patients and AD mice. In mouse bone marrow-derived DCs, Ccr7 expression was inhibited by 5-aza-2-deoxycytidine, a methylation inhibitor. Furthermore, in mouse skin DCs, methylation of CpG sites in Ccr7 was modified by either AD induction or social defeat stress. Collectively, these findings suggest that social defeat stress exacerbates AD pathology through Dnmt1 downregulation and Ccr7 upregulation in mouse skin DCs. The data also suggest a role of DNMT1 downregulation in the exacerbation of AD pathology.

Effects of 308 nm excimer light treatment on the skin microbiome of atopic dermatitis patients

BACKGROUND

The skin microbiome has been implicated in the pathophysiology of atopic dermatitis (AD). Although 308 nm excimer light treatment is an effective phototherapy for AD, its effects on the skin microbiome currently remain unclear. Therefore, we investigated the effects of the excimer light treatment on the skin bacterial and fungal microbiome of lesional skin of AD.

METHODS

Swab samples were collected from 11 healthy controls, non-lesional and lesional skin of 11 AD patients. The excimer light treatment was administered to the lesional skin. The composition of the skin microbiome, the clinical score and skin barrier function of the lesional skin were examined before and after the treatment. The composition of the skin microbiome was determined by sequencing bacterial 16S and fungal internal transcribed spacer regions.

RESULTS

The excimer light treatment significantly changed the composition of the bacterial microbiome in the lesional skin of AD, as well as improved the clinical score and skin barrier function. The treatment increased the relative abundance of the phylum Cyanobacteria and decreased that of the phylum Bacteroidetes in lesional skin. At the species level, the treatment significantly decreased the relative abundance of Staphylococcus aureus (S aureus) in lesional skin. There was also a significant correlation between the reduction of S aureus and improvement of the clinical outcomes.

CONCLUSION

Our findings suggest that alterations of the skin microbiome with excimer light treatment, specifically the decrease in the abundance of S aureus, are partly involved in the improvement of AD lesions.

Synergistic Effects of the 308-nm Excimer Light and Topical Calcipotriol for the Treatment of Chronic Hand Eczema: A Randomized Controlled Study

BACKGROUND

Though topical corticosteroid is a standard treatment for chronic hand eczema (CHE), it can cause many adverse effects. Topical calcipotriol and monochromatic 308-nm excimer light (MEL) are new alternative therapies for several dermatoses, including CHE.

OBJECTIVE

This study aims to compare the efficacy of the combination of MEL and topical calcipotriol versus topical calcipotriol alone.

METHODS

One hand of the participants was randomly assigned to be irradiated with MEL twice weekly and topical calcipotriol applied twice daily while the other hand was assigned to receive only topical calcipotriol twice daily for 8 weeks. Then, only petrolatum ointment was applied during the 4-week follow-up period. Hand Eczema Severity Index (HECSI) and modified Total Lesion Symptom Score were assessed by a blinded investigator, and a visual analogue scale score of itching symptoms was graded by the participants.

RESULTS

In total, 36 hands from 18 subjects completed the protocol. On the combination-treated sides, the mean HECSI score was significantly reduced by 25% (p = 0.015) from the 4th week. Then, it was gradually decreased to 57 and 65% (p < 0.001) at the 8th week and at the follow-up visit, respectively. For the monotherapy-treated sides, the mean HECSI score was reduced to 41% (p = 0.001) and 49% (p < 0.001) at the 8th and 12th week, accordingly. At the end of the treatment period, itching scores were significantly decreased by around 64% (p < 0.001) and 51% (p = 0.002) on the combination-treated and the monotherapy-treated sides. No serious and persistent adverse reactions were found.

CONCLUSION

The combined MEL and topical calcipotriol may be considered as an alternatively effective treatment for CHE.