Severity scores, itch scores and plasma substance P levels in atopic dermatitis treated with standard topical therapy with oral olopatadine hydrochloride

Atopic Dermatitis Itch: Scratching for an Explanation

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

Relationship of Substance P with the Degree of Atopic Dermatitis Severity

Introduction

Atopic dermatitis (AD) is a chronic inflammatory skin disease that starts during childhood with a varied course. Itching or incessant itching in severe cases, sleep disturbance, and infection-prone skin are the typical symptoms of this disease. Substance P is postulated to have an important role in AD. Increasing levels of substance P in AD induce the release of IFN-γ, IL-4, tumor necrosis factor-α (TNF-α), and IL-10 from peripheral blood mononuclear leukocytes, inducing an itching response.

Methods

This study is a cross-sectional study that aims to analyze the relationship between serum substance P levels and AD severity in children using Score of AD (SCORAD), and to determine the mean serum substance P levels and severity of AD in patients with AD. This study also aims to find out the correlation of substance P levels with the SCORAD values.

Results

Forty-six children (29 males; 17 females) with a mean age of 10.35 years (standard deviation (SD) = 4.01) were diagnosed with AD. The SCORAD index assessment was conducted to analyze AD (mean value, 23.15; SD = 9.42), and mild AD obtained the highest degree. The level of substance P was also examined (mean value, 300.88; SD = 127.55).

Discussion

This study did not find a significant relationship between substance P levels and AD severity (p-value = 0.880), and there was no significant correlation between substance P levels and SCORAD values (p-value = 0.233; r = −0.179). The limitations of this study include a small number of cases, no control group, and we only found two cases of severe AD. To generalize the results, further studies with wide range population and AD severity might be done in the future.

Involvement of Neuro-Immune Interactions in Pruritus With Special Focus on Receptor Expressions

Pruritus is a common, but very challenging symptom with a wide diversity of underlying causes like dermatological, systemic, neurological and psychiatric diseases. In dermatology, pruritus is the most frequent symptom both in its acute and chronic form (over 6 weeks in duration). Treatment of chronic pruritus often remains challenging. Affected patients who suffer from moderate to severe pruritus have a significantly reduced quality of life. The underlying physiology of pruritus is very complex, involving a diverse network of components in the skin including resident cells such as keratinocytes and sensory neurons as well as transiently infiltrating cells such as certain immune cells. Previous research has established that there is a significant crosstalk among the stratum corneum, nerve fibers and various immune cells, such as keratinocytes, T cells, basophils, eosinophils and mast cells. In this regard, interactions between receptors on cutaneous and spinal neurons or on different immune cells play an important role in the processing of signals which are important for the transmission of pruritus. In this review, we discuss the role of various receptors involved in pruritus and inflammation, such as TRPV1 and TRPA1, IL-31RA and OSMR, TSLPR, PAR-2, NK1R, H1R and H4R, MRGPRs as well as TrkA, with a focus on interaction between nerve fibers and different immune cells. Emerging evidence shows that neuro-immune interactions play a pivotal role in mediating pruritus-associated inflammatory skin diseases such as atopic dermatitis, psoriasis or chronic spontaneous urticaria. Targeting these bidirectional neuro-immune interactions and the involved pruritus-specific receptors is likely to contribute to novel insights into the underlying pathogenesis and targeted treatment options of pruritus.

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.

NK-1 Receptor Antagonists and Pruritus: Review of Current Literature

The discovery of the first neurokinin 1 (NK-1) receptor antagonist was a turning point in the prevention of chemotherapy-induced nausea and vomiting. The NK-1 antagonists are a novel class of drugs that possess antidepressant, anxiolytic, and antiemetic properties. Recently, clinicians have also described an anti-itch activity of NK-1 antagonists. We present herein results from currently available data on use of NK-1R antagonists in dermatology. For this purpose, a systemic electronic literature search of the PubMed and CINAHL databases, Cochrane Library, and clinicaltrials.gov website was performed. Based on currently available data, it can be concluded that NK-1 inhibitors show significant antipruritic potential for treatment of chronic pruritus in different dermatological conditions, but further studies are needed to establish the best indications and dosage of these drugs.

Tachykinin upregulation in atopic dermatitis

Context: Atopic dermatitis (AD) is a chronic, inflammatory, itching skin disorder, which may worsen due to stress, depression and anxiety. Tachykinins may be involved in inflammation signaling as well as they may have a role in stress, depression and anxiety. Objective: This study aimed to measure the expression of tachykinin markers, in the skin of patients with AD, and the correlation of these tachykinins with clinical and psychodemographic parameters. Materials and methods: Twenty-eight adult patients with AD were investigated regarding tachykinin expression in skin biopsies, using an immunohistochemical technique. The patients were characterized with clinical and psychodemographic parameters. Results: The number of substance P and neurokinin (NK)A positive nerve fibers, as well as NKA positive mononuclear dermal cells, was increased in lesional compared to non-lesional skin. Interestingly, the depression score and the number of dermal NK-1 receptor (R) positive cells in lesional as well as in non-lesional skin showed a correlation. Conclusion: These findings indicate an upregulation of the tachykinergic system in the inflamed skin of AD.

Hataedock treatment has preventive therapeutic effects for atopic dermatitis through skin barrier protection in Dermatophagoides farinae-induced NC/Nga mice

ETHNOPHARMACOLOGICAL RELEVANCE

Hataedock treatment is traditionally used for the purpose of preventing the future skin disease by feeding herbal extracts to the newborn in traditional Chinese and Korean medicine.

AIM OF THE STUDY

This study investigated the preventive therapeutic effects of Hataedock (HTD) treatment for atopic dermatitis (AD) through skin barrier protection in Dermatophagoides farinae-induced NC/Nga mice.

MATERIALS AND METHODS

To the HTD treatment group, the extract of Coptis japonica Makino and Glycyrrhiza uralensis Fischer, which analyzed with High Performance Liquid Chromatography (HPLC)-fingerprint for quality consistency, was administered orally to the 3-week-old mice before inducing AD. After that, Dermatophagoides farinae was applied except the control group to induce AD-like skin lesions. We confirmed the effects of HTD on morphological changes, protection of skin barrier, regulation of Th2 differentiation, inflammation regulation and induction of apoptosis through histochemistry, immunohistochemistry, and Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay.

RESULTS

HTD effectively reduced edema, angiogenesis and skin lesion. HTD also increased the levels of liver X receptor (LXR) and filaggrin but decreased the level of protein kinase C (PKC) (p<0.01). The levels of interleukin-4 (IL-4), IL-13, signal transducer and activator of transcription-6 (STAT-6) and Cluster of differentiation 40 (CD40) were significantly reduced in the HTD treated group (p<0.01). HTD also suppressed the mast cell degranulation and the level of the high-affinity IgE receptor (FcɛRI), substance P, Matrix metalloproteinases-9 (MMP-9) and 5-hydroxytryptamine (5-HT) (p<0.01). The levels of inflammatory factors such as nuclear factor-kappaB (NF-κB) p65, phosphorylated IκB (p-IκB) and inducible nitric oxide synthase (iNOS) were also decreased (p<0.01). Apoptosis of inflammatory cells was also found to increase (p<0.01).

CONCLUSION

Our results indicate that HTD effectively regulate the Th2 differentiation, mast cell activation and various inflammatory responses on AD-induced mice through protection of skin barrier. Therefore, HTD may have potential applications for alternative and preventive treatment in the management of AD.

Effect of Substance P in Staphylococcus aureus and Staphylococcus epidermidis Virulence: Implication for Skin Homeostasis

Staphylococcus aureus and Staphylococcus epidermidis are two major skin associated bacteria, and Substance P (SP) is a major skin neuropeptide. Since bacteria are known to sense and response to many human hormones, we investigated the effects of SP on Staphylococci virulence in reconstructed human epidermis model and HaCaT keratinocytes. We show that SP is stimulating the virulence of S. aureus and S. epidermidis in a reconstructed human epidermis model. qRT-PCR array analysis of 64 genes expressed by keratinocytes in the response to bacterial infection revealed a potential link between the action of SP on Staphylococci and skin physiopathology. qRT-PCR and direct assay of cathelicidin and human β-defensin 2 secretion also provided that demonstration that the action of SP on bacteria is independent of antimicrobial peptide expression by keratinocytes. Considering an effect of SP on S. aureus and S. epidermidis, we observed that SP increases the adhesion potential of both bacteria on keratinocytes. However, SP modulates the virulence of S. aureus and S. epidermidis through different mechanisms. The response of S. aureus is associated with an increase in Staphylococcal Enterotoxin C2 (SEC2) production and a reduction of exolipase processing whereas in S. epidermidis the effect of SP appears mediated by a rise in biofilm formation activity. The Thermo unstable ribosomal Elongation factor Ef-Tu was identified as the SP-interacting protein in S. aureus and S. epidermidis. SP appears as an inter-kingdom communication factor involved in the regulation of bacterial virulence and essential for skin microflora homeostasis.

Immune Pathways in Atopic Dermatitis, and Definition of Biomarkers through Broad and Targeted Therapeutics

Atopic dermatitis (AD) is the most common inflammatory skin disease. Recent research findings have provided an insight into the complex pathogenic mechanisms involved in this disease. Despite a rising prevalence, effective and safe therapeutics for patients with moderate-to-severe AD are still lacking. Biomarkers of lesional, nonlesional skin, and blood have been developed for baseline as well as after treatment with broad and specific treatments (i.e., cyclosporine A and dupilumab). These biomarkers will help with the development of novel targeted therapeutics and assessment of disease reversal, with the promise of a more personalized treatment approach. Since AD involves more than one subtype (i.e., intrinsic/extrinsic, pediatric/adult, etc.), these molecular fingerprints needs to be validated in all subpopulations with AD.

NK-1 Antagonists and Itch

Substance P (SP) is an important mediator of pro-inflammatory mechanisms in the skin. It targets multiple cells such as keratinocytes, mast cells, and fibroblasts which are involved in the cutaneous generation of pruritus. This suggests that SP is an interesting target for therapy. In fact, in recent case reports and case series, SP antagonists demonstrated a significant antipruritic effect in acute and chronic pruritus such as drug-induced pruritus, paraneoplastic pruritus, prurigo nodularis, cutaneous T-cell lymphoma, and brachioradial pruritus.

Research in practice: substance P antagonism in chronic pruritus

Pruritus is an unpleasant sensation of the skin, which triggers a desire to scratch or rub. The chronic form (≥6 weeks' duration) often occurs as a side effect of many diseases and is usually accompanied by a high loss in quality of life for patients, especially in cases in which the symptom is chronic without adequate treatment options. In recent years, the situation improved continuously, guidelines for chronic pruritus have been defined and standard medications have been proposed. For many reasons, there are still patients who are unable to obtain relief. New therapeutic approaches are therefore urgently needed. Blocking the neuropeptide substance P is a promising strategy; substance P mediates clinically relevant pro-inflammatory effects by binding to the neurokinin 1 receptor (NK-1R). This led us to hypothesize that NK-1R antagonists are promising therapeutic options for chronic pruritus. Several international case series have meanwhile proven the antipruritic effect of the NK-1R antagonist aprepitant for various forms of chronic pruritus. Initiation of clinical trials with new NK-1R-antagonists as a new therapeutic option continues this trend.

Effects of a skin neuropeptide (substance p) on cutaneous microflora

Background

Skin is the largest human neuroendocrine organ and hosts the second most numerous microbial population but the interaction of skin neuropeptides with the microflora has never been investigated. We studied the effect of Substance P (SP), a peptide released by nerve endings in the skin on bacterial virulence.

Methodology/Principal Findings

Bacillus cereus, a member of the skin transient microflora, was used as a model. Exposure to SP strongly stimulated the cytotoxicity of B. cereus (+553±3% with SP 10⁻⁶ M) and this effect was rapid (<5 min). Infection of keratinocytes with SP treated B. cereus led to a rise in caspase1 and morphological alterations of the actin cytoskeleton. Secretome analysis revealed that SP stimulated the release of collagenase and superoxide dismutase. Moreover, we also noted a shift in the surface polarity of the bacteria linked to a peel-off of the S-layer and the release of S-layer proteins. Meanwhile, the biofilm formation activity of B. cereus was increased. The Thermo unstable ribosomal Elongation factor (Ef-Tu) was identified as the SP binding site in B. cereus. Other Gram positive skin bacteria, namely Staphylococcus aureus and Staphylococcus epidermidis also reacted to SP by an increase of virulence. Thermal water from Uriage-les-Bains and an artificial polysaccharide (Teflose®) were capable to antagonize the effect of SP on bacterial virulence.

Conclusions/Significance

SP is released in sweat during stress and is known to be involved in the pathogenesis of numerous skin diseases through neurogenic inflammation. Our study suggests that a direct effect of SP on the skin microbiote should be another mechanism.

Psychoneuroimmunology of psychological stress and atopic dermatitis: pathophysiologic and therapeutic updates

Atopic dermatitis is a chronic inflammatory skin disease characterized by impaired epidermal barrier function, inflammatory infiltration, extensive pruritus and a clinical course defined by symptomatic flares and remissions. The mechanisms of disease exacerbation are still poorly understood. Clinical occurrence of atopic dermatitis is often associated with psychological stress. In response to stress, upregulation of neuropeptide mediators in the brain, endocrine organs, and peripheral nervous system directly affect immune and resident cells in the skin. Lesional and non-lesional skin of patients with atopic dermatitis demonstrates increased mast cells and mast cell-nerve fiber contacts. In the setting of stress, sensory nerves release neuromediators that regulate inflammatory and immune responses, as well as barrier function. Progress towards elucidating these neuroimmune connections will refine our understanding of how emotional stress influences atopic dermatitis. Moreover, psychopharmacologic agents that modulate neuronal receptors or the amplification circuits of inflammation are attractive options for the treatment of not only atopic dermatitis, but also other stress-mediated inflammatory skin diseases.

Plasma substance P levels in patients with persistent cough

BACKGROUND

Substance P (SP) is involved in the pathogenesis of cough in animal models. However, few studies in humans have been reported and the roles of SP in clinical cough remain obscure.

OBJECTIVES

To clarify the relevance of plasma levels of SP in patients with persistent cough.

METHODS

We studied 82 patients with cough persisting for at least 3 weeks and 15 healthy controls. Patients were classified as having asthmatic cough (cough-variant asthma and cough-predominant asthma; n = 61) or nonasthmatic cough (n = 21; postinfectious cough, n = 6; gastroesophageal reflux disease, n = 5; idiopathic cough, n = 5, and others, n = 5). Correlations were evaluated between plasma SP levels as measured with ELISA and methacholine airway hyperresponsiveness (airway sensitivity and airway reactivity), capsaicin cough sensitivity, sputum eosinophil and neutrophil counts, and pulmonary function.

RESULTS

Plasma SP levels were significantly elevated in patients with both asthmatic and nonasthmatic cough compared with controls [31.1 pg/ml (range 18.0-52.2) and 30.0 pg/ml (range 15.1-50.3) vs. 15.4 pg/ml (range 11.3-23.7); p = 0.003 and p = 0.038, respectively] but did not differ between the two patient groups (p = 0.90). Plasma SP levels correlated with airway sensitivity (threshold dose of methacholine) in the patients with asthmatic cough (r = -0.37, p = 0.005) but not with airway reactivity, cough sensitivity, FEV1 values, or sputum eosinophil and neutrophil counts in either group.

CONCLUSIONS

Increased levels of SP in plasma are associated with persistent cough in humans and might be related to airway sensitivity in asthmatic cough.