Effects of Psychological Stress on Spontaneous Itch and Mechanical Alloknesis of Atopic Dermatitis

Atopic dermatitis (AD), a chronic inflammatory skin disease, manifests as an intractable itch. Psychological stress has been suggested to play a role in the onset and worsening of AD symptoms. However, the pathophysiological relationships between psychological stressors and cutaneous manifestations remain unclear. To elucidate the mechanisms underlying the stress-related exacerbation of itch, we investigated the effects of water stress, restraint stress and repeated social defeat stress on itch-related scratching behaviour, mechanical alloknesis and dermatitis in male NC/Nga mice with AD-like symptoms induced by the repeated application of ointment containing Dermatophagoides farina body. NC/Nga mice with AD-like symptoms were subjected to water stress, restraint stress and repeated social defeat stress, and their scratching behaviour, sensitivity to mechanical stimuli (mechanical alloknesis) and severity of  dermatitis were evaluated. Social defeat stress+ Dermatophagoides farina body-treated mice exposed to stress showed slower improvements in or the exacerbation of AD-like symptoms, including dermatitis and itch. In the mechanical alloknesis assay, the mechanical alloknesis scores of social defeat stress+ Dermatophagoides farina body-treated mice exposed to stress were significantly higher than those of non-exposed social defeat stress+ Dermatophagoides farina body- and social defeat stress-treated mice. These results suggest that psychological stress delays improvements in dermatitis by exacerbating itch hypersensitivity in AD.

Vitexin inhibits pain and itch behavior via modulating TRPV4 activity in mice

Itching and pain are distinct unpleasant sensations. The transient receptor potential cation channel subfamily V member 4 (TRPV4) pathway is regarded as a shared pathway that mediates pain and itching. Vitexin (Mujingsu, MJS), a C-glycosylflavonoid, is an effective analgesic. This study aimed to explore the antinociceptive and anti-pruritic effects of MJS and whether its effects are mediated via the TRPV4 pathway. Mice were treated with MJS (7.5 mg/kg) 0.5 h prior to the initiation of the pain or itch modeling process. The results showed that MJS suppressed pain-like behavior in hot plate, thermal infiltration, glacial acetic acid twisting, and formalin tests. Administration of MJS decreased the pruritus response induced by histamine, C48/80, chloroquine and BAM8-22 within 30 min. MJS reduced scratching bouts and lessened the wiping reaction of mice under TRPV4 activation by GSK101 (10 µg/5 μl). MJS inhibited scratching behavior in acetone-ether-water (AEW)-treated mice within 60 min. An H1 receptor antagonist-chlorpheniramine (CLP, 400 mg/kg)-and a TRPV4 antagonist-HC067047 (250 ng/kg), exhibited similar effects to those of MJS. Moreover, MJS ameliorated dry skin itch-associated cutaneous barrier disruption in mice. MJS did not inhibit the expression of TRPV4 in the dorsal root ganglion neurons at L2-L3 in AEW mice. These results indicate that the analgesic and anti-pruritic effects of MJS in acute and chronic pain and itching, as well as itching caused by TRPV4 activation, could be attributed to the TRPV4 pathway modulation.

Upregulation of DRG protein TMEM100 facilitates dry-skin-induced pruritus by enhancing TRPA1 channel function

The dry skin tortures numerous patients with severe itch. The transient receptor potential cation channel V member 1 (TRPV1) and A member 1 (TRPA1) are two essential receptors for peripheral neural coding of itch sensory, mediating histaminergic and nonhistaminergic itch separately. In the dorsal root ganglion, transmembrane protein 100 (TMEM100) is structurally related to both TRPV1 and TRPA1 receptors, but the exact role of TMEM100 in itch sensory coding is still unknown. Here, in this study, we find that TMEM100 ⁺ DRG neurons account for the majority of activated neurons in an acetone-ether-water (AEW)-induced dry skin itch model, and some TMEM100 ⁺ DRG neurons are colocalized with both TRPA1 and the chloroquine-related Mrgpr itch receptor family. Both the expression and function of TRPA1 channels, but not TRPV1 channels, are upregulated in the AEW model, and specific DRG Tmem100 gene knockdown alleviates AEW-induced itch and rescues the expression and functional changes of TRPA1. Our results strongly suggest that TMEM100 protein in DRG is the main facilitating factor for dry-skin-related chronic itch, and specific suppression of TMEM100 in DRG could be a novel effective treatment strategy for patients who suffer from dry skin-induced itch.

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.

When topical therapy of atopic dermatitis fails: a guide for the clinician

INTRODUCTION

While topical medications are the first line of treatment for mild-to-moderate atopic dermatitis, they are ineffective in individuals with diffuse disease and moderate-to-severe atopic itch. For these individuals, as well as those who do not respond to topical treatments, systemic medicines are typically essential and helpful.

AREAS COVERED

We conducted a review of the literature to identify established systemic therapies, novel biologic agents, and recent advances in the pathophysiology of atopic dermatitis. The review discusses these data, which show that the majority of atopic itch medications now in development target the type 2 immune axis and brain sensitization, two main etiologies of atopic itch. We emphasize the evidence, efficacy, and side effect profiles of currently available systemic medications for atopic itch, as well as future potential for tailored therapy.

EXPERT OPINION

We give our professional opinion on the current state of knowledge about atopic eczema pathogenesis and the innovative targets and therapies for atopic itch that include MRGPRX2, periostin, gabaergic medicines, and JAK/STAT inhibitors. Additionally, we discuss patient populations that stand to benefit the most from targeting these molecules or utilizing these drugs, as well as those who may face a disproportionate weight of adverse effects.

Peripheral endomorphins drive mechanical alloknesis under the enzymatic control of CD26/DPPIV

BACKGROUND

Mechanical alloknesis (or innocuous mechanical stimuli-evoked itch) often occurs in dry skin-based disorders such as atopic dermatitis and psoriasis. However, the molecular and cellular mechanisms underlying mechanical alloknesis remain unclear. We recently reported the involvement of CD26 in the regulation of psoriatic itch. This molecule exhibits dipeptidyl peptidase IV (DPPIV) enzyme activity and exerts its biologic effects by processing various substances, including neuropeptides.

OBJECTIVE

The aim of the present study was to investigate the peripheral mechanisms of mechanical alloknesis by using CD26/DPPIV knockout (CD26KO) mice.

METHODS

We applied innocuous mechanical stimuli to CD26KO or wild-type mice. The total number of scratching responses was counted as the alloknesis score. Immunohistochemical and behavioral pharmacologic analyses were then performed to examine the physiologic activities of CD26/DPPIV or endomorphins (EMs), endogenous agonists of μ-opioid receptors.

RESULTS

Mechanical alloknesis was more frequent in CD26KO mice than in wild-type mice. The alloknesis score in CD26KO mice was significantly reduced by the intradermal administration of recombinant DPPIV or naloxone methiodide, a peripheral μ-opioid receptor antagonist, but not by that of mutant DPPIV without enzyme activity. EMs (EM-1 and EM-2), selective ligands for μ-opioid receptors, are substrates for DPPIV. Immunohistochemically, EMs were located in keratinocytes, fibroblasts, and peripheral sensory nerves. Behavioral analyses revealed that EMs preferentially provoked mechanical alloknesis over chemical itch. DPPIV-digested forms of EMs did not induce mechanical alloknesis.

CONCLUSION

The present results suggest that EMs induce mechanical alloknesis at the periphery under the enzymatic control of CD26/DPPIV.

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.

Effect of a new cryotherapy device on an itchy sensation in patients with mild atopic dermatitis

BACKGROUND

The existence of an itchy sensation is a common complaint in patients with atopic dermatitis. More therapeutic modalities to address the itchy sensation in atopic dermatitis are still required.

OBJECTIVE

We sought to assess the effect of a new cryotherapy device on the itchy sensation experienced by patients with atopic dermatitis.

METHODS

A total of 28 patients with mild to moderate atopic dermatitis participated in this study. A split-body clinical trial was conducted for 2 months, where one side of each participant was treated with the novel cryotherapy device, and the other side of each participant was observed as a control. The cryotherapy device was set to -5°C and applied for five seconds. We evaluated the visual analog scale (VAS) score for itch at 10, 30, and 60 minutes and at 1, 2 and 8 weeks after cryotherapy application. In addition, the level of patient satisfaction and adverse events were evaluated every visit.

RESULTS

On the day immediately after treatment, the VAS score for itch in the treated-side group was lower following cryotherapy application than as compared within the control-side group. Further, the VAS score for itch in the treated-side group at baseline (before treatment) was higher than at 1, 2 and 8 weeks after treatment. The proportion of patients reporting good or excellent satisfaction was 14.3%. No serious adverse events were recorded.

CONCLUSIONS

The novel cryotherapy tested herein may be a valuable antipruritic therapeutic remedy in patients with atopic dermatitis.

Cutaneous sensitivity modulation by Aquaphilus dolomiae extract-G3 on in vitro models of neuro-inflammation

BACKGROUND

Inflammatory skin disorders, including atopic dermatitis (AD), associated pruritus and sensitive skin, have a complex multifactorial pathogenesis including neurogenic inflammation involving the release in blood and skin of neurotransmitters such as substance P (SP).

AIMS AND METHODS

In vitro models evaluated the effect of the original biological extract of Aquaphilus dolomiae extract-G3 (ADE-G3) on cutaneous neurogenic inflammation.

RESULTS

ADE-G3 significantly inhibited SP-stimulated release of IL-1β and TNF-α from normal human epidermal keratinocytes; significantly and dose-dependently inhibited SP-stimulated activation of human mast cells; significantly inhibited veratridine-stimulated release of SP from human sensory neurons; modulated expression of genes involved in lipid synthesis, innate immunity, corneocyte scaffolding and epidermal differentiation in a histamine-sensitized reconstructed human epidermis model; and, when applied topically to ex vivo human explants, inhibited IL-8 and histamine release.

CONCLUSIONS

Topically applied ADE-G3, once formulated, may improve neuro-inflammation in patients with inflammatory skin disorders.

Dupilumab: Basic aspects and applications to allergic diseases

Interleukin (IL)-4 and IL-13, signature type 2 cytokines, exert their actions by binding to two types of receptors sharing the IL-4R α chain (IL-4Rα). Since IL-4 and IL-13 play important and redundant roles in the pathogenesis of allergic diseases, blocking both the IL-4 and IL-13 signals would be a powerful and effective strategy for treating allergic diseases. Dupilumab (Dupixent®) is a fully human monoclonal antibody recognizing IL-4Rα and blocking both the IL-4 and IL-13 signals. Dupilumab was first prescribed for atopic dermatitis (AD) patients and has been widely approved for adult patients with moderate to severe AD since 2018. Dupilumab has since been used for asthma, receiving approval for uncontrolled asthma in 2019. A phase 3 study using dupilumab for chronic rhinosinusitis with nasal polyps (CRSwNP) has been just completed, with positive results. Several clinical trials of dupilumab for other diseases in which type 2 inflammation is dominant are now underway. It is hoped that dupilumab will open the door to a new era for treating allergic patients with AD, asthma, and CRSwNP, and for more patients with type 2 inflammations.

Neuronal hyperexcitability and astrocyte activation in spinal dorsal horn of a dermatitis mouse model with cutaneous hypersensitivity

Cleaning products such as soaps, shampoos, and detergents are comprised mainly of surfactants, agents known to cause dermatitis and cutaneous hypersensitivity characterized by itching, stinging, and burning of the skin and scalp. However, the mechanisms underlying surfactant-induced cutaneous hypersensitivity remain unclear. In the present study, we investigated the mechanisms of cutaneous hypersensitivity in mice treated with the detergent sodium dodecyl sulfate (SDS). Repeated SDS application to the skin induced inflammation, xeroderma, and elongation of peripheral nerves into the epidermis. The number of neurons immunopositive for c-Fos, a well known marker of neural activity, was substantially higher (+441%) in spinal dorsal horn (SDH) lamina I-II (but not lamina III-VI) of SDS-treated mice compared to vehicle-treated mice. In vivo extracellular recording revealed enhanced spontaneous (+64%) and non-noxious mechanical stimulation-evoked firing (+139%) of SDH lamina I-II neurons in SDS-treated mice, and stimulation-evoked neuronal firing was sustained (+5333%) even after stimulation. The number of GFAP-positive (activated) astrocytes, but not Iba1-positive microglia, was also elevated (+137%) in SDH lamina I-II of SDS-treated mice compared to vehicle-treated mice. Peripheral nerve elongation and hyperexcitability of afferent or SDH neurons, possible associated with the activation of spinal astrocytes, may underlie cutaneous hypersensitivity induced by surfactants.

Neutrophils promote CXCR3-dependent itch in the development of atopic dermatitis

Chronic itch remains a highly prevalent disorder with limited treatment options. Most chronic itch diseases are thought to be driven by both the nervous and immune systems, but the fundamental molecular and cellular interactions that trigger the development of itch and the acute-to-chronic itch transition remain unknown. Here, we show that skin-infiltrating neutrophils are key initiators of itch in atopic dermatitis, the most prevalent chronic itch disorder. Neutrophil depletion significantly attenuated itch-evoked scratching in a mouse model of atopic dermatitis. Neutrophils were also required for several key hallmarks of chronic itch, including skin hyperinnervation, enhanced expression of itch signaling molecules, and upregulation of inflammatory cytokines, activity-induced genes, and markers of neuropathic itch. Finally, we demonstrate that neutrophils are required for induction of CXCL10, a ligand of the CXCR3 receptor that promotes itch via activation of sensory neurons, and we find that that CXCR3 antagonism attenuates chronic itch.

Chronic itch is a debilitating disorder that can last for months or years. Eczema, or atopic dermatitis, is the most common cause for chronic itch, affecting one in ten people worldwide. Many treatments for the condition are ineffective, and the exact cause of the disease is unknown, but many different types of cells are likely involved. These include skin cells and inflammation-promoting immune cells, as well as nerve cells that detect inflammation, relay itch and pain information to the brain, and regulate the immune system.

Learning more about how these cells interact in eczema may help scientists find better treatments for the condition. So far, a lot of research has focused on static ‘snapshots’ of mature eczema lesions from human skin or animal models. These studies have identified abnormalities in genes or cells, but have not revealed how these genes and cells interact over time to cause chronic itch and inflammation.

Now, Walsh et al. reveal that immune cells called neutrophils trigger chronic itch in eczema. The experiments involved mice with a condition that mimics eczema, and showed that removing the neutrophils in these mice alleviated their itching. They also showed that dramatic and rapid changes occur in the nervous system of mice suffering from the eczema-like condition. For example, excess nerves grow in the animals’ damaged skin, genes in the nerves that detect sensations become hyperactive, and changes occur in the spinal cord that have been linked to nerve pain. When neutrophils are absent, these changes do not take place.

These findings show that neutrophils play a key role in chronic itch and inflammation in eczema. Drugs that target neutrophils, which are already used to treat other diseases, might help with chronic itch, but they would need to be tested before they can be used on people with eczema.

Neurite Outgrowth and Morphological Changes Induced by 8-trans Unsaturation of Sphingadienine in kCer Molecular Species

Konjac ceramide (kCer), which consists of plant-type molecular species of characteristic shingoid bases and fatty acids, is prepared from konjac glucosylceramide GlcCer by chemoenzymatical deglucosylation. kCer activates the semaphorin 3A (Sema3A) signaling pathway, inducing collapsin response mediator protein 2 (CRMP2) phosphorylation. This results in neurite outgrowth inhibition and morphological changes in remaining long neurites in PC12 cells. Whether a specific molecular species of kCer can bind to the Sema3A receptor (Neuropilin1, Nrp1) and activate the Sema3A signaling pathway remains unknown. Here, we prepared kCer molecular species using endoglycoceramidase I-mediated deglucosylation and examined neurite outgrowth and phosphorylation of collapsin response mediator protein 2 in nerve growth factor (NGF)-primed cells. The 8-trans unsaturation of sphingadienine of kCer was essential for Sema3A-like signaling pathway activation. Conversely, 8-cis unsaturation of kCer molecular species had no effect on Sema3A-like activation, and neurite outgrowth inhibition resulted in remaining short neurites. In addition, α-hydroxylation of fatty acids was not associated with the Sema3A-like activity of the kCer molecular species. These results suggest that 8-trans or 8-cis isomerization of sphingadienine determines the specific interactions at the ligand-binding site of Nrp1.

Mast cell tetrahydrobiopterin contributes to itch in mice

GTP cyclohydrolase (GCH1) governs de novo synthesis of the enzyme cofactor, tetrahydrobiopterin (BH4), which is essential for biogenic amine production, bioactive lipid metabolism and redox coupling of nitric oxide synthases. Overproduction of BH4 via upregulation of GCH1 in sensory neurons is associated with nociceptive hypersensitivity in rodents, and neuron-specific GCH1 deletion normalizes nociception. The translational relevance is revealed by protective polymorphisms of GCH1 in humans, which are associated with a reduced chronic pain. Because myeloid cells constitute a major non-neuronal source of BH4 that may contribute to BH4-dependent phenotypes, we studied here the contribution of myeloid-derived BH4 to pain and itch in lysozyme M Cre-mediated GCH1 knockout (LysM-GCH1-/- ) and overexpressing mice (LysM-GCH1-HA). Unexpectedly, knockout or overexpression in myeloid cells had no effect on nociceptive behaviour, but LysM-driven GCH1 knockout reduced, and its overexpression increased the scratching response in Compound 48/80 and hydroxychloroquine-evoked itch models, which involve histamine and non-histamine dependent signalling pathways. Mechanistically, GCH1 overexpression increased BH4, nitric oxide and hydrogen peroxide, and these changes were associated with increased release of histamine and serotonin and degranulation of mast cells. LysM-driven GCH1 knockout had opposite effects, and pharmacologic inhibition of GCH1 provided even stronger itch suppression. Inversely, intradermal BH4 provoked scratching behaviour in vivo and BH4 evoked an influx of calcium in sensory neurons. Together, these loss- and gain-of-function experiments suggest that itch in mice is contributed by BH4 release plus BH4-driven mediator release from myeloid immune cells, which leads to activation of itch-responsive sensory neurons.

Conopeptides promote itch through human itch receptor hMgprX1

Members of Mas related G-protein coupled receptors (Mrgpr) are known to mediate itch. To date, several compounds have been shown to activate these receptors, including chloroquine, a common antimalarial drug, and peptides of the RF-amide family. However, specific ligands for these receptors are still lacking and there is a need for novel compounds that can be used to modulate the receptors in order to understand the cellular and molecular mechanism in which they mediate itch. Some cone snail venoms were previously shown to induce itch in mice. Here, we show that the venom of Conus textile induces itch through activation of itch-sensing sensory neurons, marked by their sensitivity to chloroquine. Two RF-amide peptides, CNF-Tx1 and CNF-Tx2, were identified in a C. textile venom gland transcriptome. These belong to the conorfamide family of peptides which includes previously described peptides from the venoms of Conus victoriae (CNF-Vc1) and Conus spurius (CNF-Sr1 and CNF-Sr2). We show that CNF-Vc1 and CNF-Sr1 activate MrgprC11 whereas CNF-Vc1 and CNF-Tx2 activate the human MrgprX1 (hMrgprX1). The peptides CNF-Tx1 and CNF-Sr2 do not activate MrgprC11 or hMrgprX1. Intradermal injection of CNF-Vc1 and CNF-Tx2 into the cheek of a transgenic mouse expressing hMrgprX1 instead of endogenous mouse Mrgprs resulted in itch-related scratching thus demonstrating the in vivo activity of these peptides. Using truncated analogues of CNF-Vc1, we identified amino acids at positions 7-14 as important for activity against hMrgprX1. The conopeptides reported here are tools that can be used to advance our understanding of the cellular and molecular mechanism of itch mediated by Mrgprs.

Substance P restores normal skin architecture and reduces epidermal infiltration of sensory nerve fiber in TNCB-induced atopic dermatitis-like lesions in NC/Nga mice

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disorder characterized by intense pruritus and eczematous lesion. Substance P (SP) is an 11-amino-acid endogenous neuropeptide that belongs to the tachykinin family and several reports recently have supported the anti-inflammatory and tissue repairing roles of SP.

OBJECTIVE

In this study, we investigated whether SP can improve AD symptoms, especially the impaired skin barrier function, in 2, 4, 6-trinitrochlorobenzene (TNCB)-induced chronic dermatitis of NC/Nga mice or not.

METHOD

AD-like dermatitis was induced in NC/Nga mice by repeated sensitization with TNCB for 5 weeks. The experimental group designations and topical treatments were as follows: vehicle group (AD-VE); SP group (AD-SP); and SP with NK1R antagonist CP99994 (AD-SP-A) group. Histological analysis was performed to evaluate epidermal differentiation, dermal integrity, and epidermal nerve innervation in AD-like lesions. The skin barrier functions and pruritus of NC/Nga mice were evaluated by measuring transepidermal water loss (TEWL) and scratching behavior, respectively.

RESULT

Topical SP treatment resulted in significant down-regulation of Ki67 and the abnormal-type keratins (K) K6, K16, and K17, restoration of filaggrin and claudin-1, marked reduction of TEWL, and restoration of basement membrane and dermal collagen deposition, even under continuous sensitization of low dose TNCB. In addition, SP significantly reduced innervation of itch-evoking nerve fibers, gelatinase activity and nerve growth factor (NGF) expression in the epidermis but upregulated semaphorin-3A (Sema3A) expression in the epidermis, along with reduced scratching behavior in TNCB-treated NC/Nga mice. All of these effects were completely reversed by co-treatment with the NK1R antagonist CP99994. In cultured human keratinocytes, SP treatment reduced expression of TGF-α, but upregulated TGF-β and Sema3A.

CONCLUSION

Topically administered SP can restore normal skin barrier function, reduce epidermal infiltration of itch-evoking nerve fibers in the AD-like skin lesions, and alleviate scratching behavior. Thus, SP may be proposed as a potential medication for chronic dermatitis and AD.

Relationships among plasma granzyme B level, pruritus and dermatitis in patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease characterized by skin barrier dysfunction, allergic inflammation and intractable pruritus resistant to conventional antipruritic treatments, including H₁-antihistamines. Granzymes (Gzms) are a family of serine proteases expressed by cytotoxic T lymphocytes and natural killer cells that have been shown to modulate inflammation. However, the relationship between Gzms and pathology in AD remains unclear.

OBJECTIVE

This study assessed the correlation between plasma GzmB levels and severity of pruritus and dermatitis, in AD patients.

METHODS

Plasma was collected from 46 patients with AD, 24 patients with psoriasis, and 30 healthy controls. AD severity was assessed with the scoring atopic dermatitis (SCORAD) index, psoriasis severity with the psoriasis area and severity index (PASI), and degree of pruritus by visual analogue scale (VAS) score. GzmA, GzmB and gastrin releasing peptide (GRP) levels were measured by enzyme-linked immunosorbent assays.

RESULTS

Plasma GzmB concentrations were significantly higher in patients with AD and psoriasis than in healthy controls. Correlation analyses showed that plasma GzmB concentrations positively correlated with SCORAD and serum levels of severity markers such as thymus and activation-regulated chemokine, and lactate dehydrogenase in AD patients. Moreover, plasma levels of GRP, an itch-related peptide, were higher in patients with AD, positively correlating with VAS score and plasma GzmB level. In addition, plasma GzmB concentration was significantly lower in the treatment group than the untreated group with AD. Meanwhile, there were no correlations among GzmB levels, VAS score and PASI score in patients with psoriasis. In contrast to the results of plasma GzmB, plasma GzmA levels were unchanged among AD, psoriasis and healthy groups, and showed no correlations with VAS score and SCORAD index in patients with AD.

CONCLUSION

Plasma GzmB levels may reflect the degree of pruritus and dermatitis in patients with AD.

Atopic dermatitis: allergic dermatitis or neuroimmune dermatitis?

Advances in knowledge of neurocellulars relations have provided new directions in the understanding and treatment of numerous conditions, including atopic dermatitis. It is known that emotional, physical, chemical or biological stimuli can generate more accentuated responses in atopic patients than in non-atopic individuals; however, the complex network of control covered by these influences, especially by neuropeptides and neurotrophins, and their genetic relations, still keep secrets to be revealed. Itching and airway hyperresponsiveness, the main aspects of atopy, are associated with disruption of the neurosensory network activity. Increased epidermal innervation and production of neurotrophins, neuropeptides, cytokines and proteases, in addition to their relations with the sensory receptors in an epidermis with poor lipid mantle, are the aspects currently covered for understanding atopic dermatitis.

Assessing the itching intensity using visual analogue scales in atopic dermatitis patients against the background of a therapy with calcineurin inhibitors

Goal. To assess the effect of topical treatment of atopic dermatitis patients with the 0.1% tacrolimus ointment on the itching intensity and skin expression level of growth factor proteins affecting the intensity of cutaneous innervation. Materials and methods. Fifteen patients suffering from atopic dermatitis underwent treatment with the 0.1% tacrolimus ointment. The SCORAD index was calculated to assess the severity of clinical manifestations. The itching intensity was assessed using a visual analogue scale. The skin expression of nerve growth factors, amphiregulin, semaphorin 3A and PGP9.5 protein (a nerve fiber marker) was assessed by the indirect immunofluorescence method. Results. An increased expression of the nerve growth factor and reduced semaphorin 3A expression levels were noted in the patients’ epidermis; there was an increase in the quantity, mean length and fluorescence intensity of PGP9.5+ nerve fibers. As a result of the treatment, the disease severity and itching intensity were reduced, the nerve growth factor expression level was reduced while semaphorin 3A expression level increased in the epidermis, and the mean length and fluorescence intensity of PGP9.5+ nerve fibers was also reduced. A positive correlation among the itching intensity and nerve growth factor expression level, quantity and mean length of PGP9.5+ nerve fibers in the epidermis was revealed, and negative correlation between the itching intensity and semaphorin 3A expression level in the epidermis was established. Conclusion. Topical treatment with the 0.1% Tacrolimus ointment reduces the itching intensity in atopic dermatitis patients, which is related to the therapy-mediated reduction in the epidermis innervation level, decreased expression of epidermal nerve growth factor and increased semaphorin 3A expression level.

Methods for preclinical assessment of antipruritic agents and itch mechanisms independent of mast-cell histamine

Itch is a sensation that provokes a desire to scratch. Mast-cell histamine was thought to be a key itch mediator. However, histamine and mast-cell degranulation were reported not to elicit scratching in animals. It was difficult to investigate the pathophysiology of itching and to evaluate the antipruritic efficacy of chemical agents in the early 1990 s. We showed that hind-paw scratching and biting were elicited by stimulation with pruritogenic agents in mice. Those results demonstrated for the first time that cutaneous itching could be evaluated behaviorally in animals. We established various animal models of pathological itch of the skin (dry skin, mosquito allergy, surfactant-induced pruritus, and herpes zoster) and mucus membranes (pollen allergy). Mast-cell histamine did not play a key role in itching in any animal model examined except for the pollen allergy model. Histamine is not an exclusive itch mediator of mast cells; tryptase and leukotriene B4 released from mast cells also act as itch mediators. Epidermal keratinocytes release several itch mediators, such as leukotriene B4, sphingosylphosphorylcholine, thromboxane A2, nociceptin, nitric oxide, and histamine, which may play important roles in pathological itching. Appropriate animal models of pathological itching are needed for pharmacological evaluation of the antipruritic efficacy of chemical agents.

Role of Ceramide from Glycosphingolipids and Its Metabolites in Immunological and Inflammatory Responses in Humans

Glycosphingolipids (GSLs) are composed of hydrophobic ceramide and hydrophilic sugar chains. GSLs cluster to form membrane microdomains (lipid rafts) on plasma membranes, along with several kinds of transducer molecules, including Src family kinases and small G proteins. However, GSL-mediated biological functions remain unclear. Lactosylceramide (LacCer, CDw17) is highly expressed on the plasma membranes of human phagocytes and mediates several immunological and inflammatory reactions, including phagocytosis, chemotaxis, and superoxide generation. LacCer forms membrane microdomains with the Src family tyrosine kinase Lyn and the Gαi subunit of heterotrimeric G proteins. The very long fatty acids C24:0 and C24:1 are the main ceramide components of LacCer in neutrophil plasma membranes and are directly connected with the fatty acids of Lyn and Gαi. These observations suggest that the very long fatty acid chains of ceramide are critical for GSL-mediated outside-in signaling. Sphingosine is another component of ceramide, with the hydrolysis of ceramide by ceramidase producing sphingosine and fatty acids. Sphingosine is phosphorylated by sphingosine kinase to sphingosine-1-phosphate, which is involved in a wide range of cellular functions, including growth, differentiation, survival, chemotaxis, angiogenesis, and embryogenesis, in various types of cells. This review describes the role of ceramide moiety of GSLs and its metabolites in immunological and inflammatory reactions in human.

Progression of itching intensity and expression of growth factor proteins in skin of people suffering from atopic dermatitis under the influence of ultraviolet phototherapy

Study of progression of itching intensity and expression of growth factor proteins in skin of people suffering from atopic dermatitis under the influence of narrowband (311Nm) phototherapy. Material and methods. 30 patients with atopic dermatitis were treated by using narrowband (311Nm) phototherapy. SCORAD index was used to assess the severity of the clinical responses. Itching intensity was assessed using visual analogue scale. Expression of growth factor of nerves, semaphorine-3A, amphiregulin, and PGP9.5, a protein marker for nerve fibers, was investigated by means of indirect immunofluorescence. Results. Increased expression level of nerves growth factor, decreased expression level of semaphorine-3A, and increase in the number, average length and luminous intensity of PGP9.5+ -nerve fibers were found in the patients’ epidermis. Course of narrowband (311 Nm) phototherapy resulted in a decrease of the severity of the disease and itching intensity, and semaphorine-3A expression increase, reduction of number and average length of nerve fibers in the epidermis. A direct correlation relationship between the itching intensity and expression level of nerve growth factor, number and average length of PGP9.5+ -nerve fibers in the epidermis as well as an inverse correlation relationship between itching intensity and expression level of semaphorine-3A in the epidermis were found. Conclusion. Treating patients suffering from atopic dermatitis with narrowband (311 Nm) phototherapy leads to a decrease of the itching intensity associated with a decreased intensity of innervation of the epidermis. This decrease in course of phototherapy is facilitated by decrease of nerve growth factor expression level and increase of semaphorine-3A expression.

Insights into bombesin receptors and ligands: Highlighting recent advances

This following article is written for Prof. Abba Kastin's Festschrift, to add to the tribute to his important role in the advancement of the role of peptides in physiological, as well as pathophysiological processes. There have been many advances during the 35 years of his prominent role in the Peptide field, not only as editor of the journal Peptides, but also as a scientific investigator and editor of two volumes of the Handbook of Biological Active Peptides [146,147]. Similar to the advances with many different peptides, during this 35 year period, there have been much progress made in the understanding of the pharmacology, cell biology and the role of (bombesin) Bn receptors and their ligands in various disease states, since the original isolation of bombesin from skin of the European frog Bombina bombina in 1970 [76]. This paper will briefly review some of these advances over the time period of Prof. Kastin 35 years in the peptide field concentrating on the advances since 2007 when many of the results from earlier studies were summarized [128,129]. It is appropriate to do this because there have been 280 articles published in Peptides during this time on bombesin-related peptides and it accounts for almost 5% of all publications. Furthermore, 22 Bn publications we have been involved in have been published in either Peptides [14,39,55,58,81,92,93,119,152,216,225,226,231,280,302,309,355,361,362] or in Prof. Kastin's Handbook of Biological Active Peptides [137,138,331].

Inhibitory Activity of Yokukansankachimpihange against Nerve Growth Factor-Induced Neurite Growth in Cultured Rat Dorsal Root Ganglion Neurons

Chronic pruritus is a major and distressing symptom of many cutaneous diseases, however, the treatment remains a challenge in the clinic. The traditional Chinese-Japanese medicine (Kampo medicine) is a conservative and increasingly popular approach to treat chronic pruritus for both patients and medical providers. Yokukansankachimpihange (YKH), a Kampo formula has been demonstrated to be effective in the treatment of itching of atopic dermatitis in Japan although its pharmacological mechanism is unknown clearly. In an attempt to clarify its pharmacological actions, in this study, we focused on the inhibitory activity of YKH against neurite growth induced with nerve growth factor (NGF) in cultured rat dorsal root ganglion (DRG) neurons because epidermal hyperinnervation is deeply related to itch sensitization. YKH showed approximately 200-fold inhibitory activity against NGF-induced neurite growth than that of neurotropin (positive control), a drug used clinically for treatment of chronic pruritus. Moreover, it also found that Uncaria hook, Bupleurum root and their chemical constituents rhynchophylline, hirsutine, and saikosaponin a, d showed inhibitory activities against NGF-induced neurite growth, suggesting they should mainly contribute to the inhibitory activity of YKH. Further study on the effects of YKH against epidermal nerve density in “itch-scratch” animal models is under investigation.

Anatomical evidence of pruriceptive trigeminothalamic and trigeminoparabrachial projection neurons in mice

Itch is relayed to higher centers by projection neurons in the spinal and medullary dorsal horn. We employed a double-label method to map the ascending projections of pruriceptive and nociceptive trigeminal and spinal neurons. The retrograde tracer fluorogold (FG) was stereotaxically injected into the right thalamus or lateral parabrachial area (LPb) in mice. Seven days later, mice received intradermal (id) microinjection of histamine, chloroquine, capsaicin, or vehicle into the left cheek. Histamine, chloroquine, and capsaicin intradermally elicited similar distributions of Fos-positive neurons in the medial aspect of the superficial medullary and spinal dorsal horn from the trigeminal subnucleus caudalis to C2. Among neurons retrogradely labeled from the thalamus, 43%, 8%, and 22% were Fos-positive following id histamine, chloroquine, or capsaicin. Among the Fos-positive neurons following pruritic or capsaicin stimuli, ∼1-2% were retrogradely labeled with FG. Trigeminoparabrachial projection neurons exhibited a higher incidence of double labeling in the superficial dorsal horn. Among the neurons retrogradely labeled from LPb, 36%, 29%, and 33% were Fos positive following id injection of histamine, chloroquine, and capsaicin, respectively. Among Fos-positive neurons elicited by id histamine, chloroquine, and capsaicin, respectively, 3.7%, 4.3%, and 4.1% were retrogradely labeled from LPb. The present results indicate that, overall, relatively small subpopulations of pruriceptive and/or nociceptive neurons innervating the cheek project to thalamus or LPb. These results imply that the vast majority of pruritogen- and algogen-responsive spinal neurons are likely to function as interneurons relaying information to projection neurons and/or participating in segmental nocifensive circuits.

Treating pediatric atopic dermatitis: current perspectives

Atopic dermatitis (AD) is a chronic, inflammatory skin condition which affects millions of people worldwide. It is most commonly seen in children but may also progress into adulthood. Management of this complex disease requires a multi-pronged approach which can address the myriad of issues which underscore its development. Avoidance of triggering factors is imperative in establishing consistent control of skin irritation while daily moisturization can be very effective in skin barrier repair and maintenance. Judicious use of anti-inflammatory medications has been shown to make a significant impact on both treatment as well as prevention of disease. Unfortunately, pruritus, a key feature of AD, has proven much harder to control. Finally, awareness of the risks of colonization and infection in patients with AD should be incorporated into their surveillance and management plans. While our understanding has progressed greatly regarding this disease, further research is still needed regarding future directions for both treatment and prevention.

Dynamics of expression rates of growth factor proteins in psoriatic patients receiving a phototherapy

Goal. To study the dynamics of expression rates of growth factor proteins in psoriatic patients receiving the PUVA therapy. Materials and methods. The authors conducted a study of 30 patients with psoriasis vulgaris treated with the PUVA therapy. The psoriasis severity and extent of itching were assessed prior to and after the treatment by the PASI index and visual analogue scale, respectively. The expression of semaphorin 3A, amphiregulin, nerve growth factor and PGP 9.5 protein (a nerve fiber marker) in the skin was assessed by the indirect immunofluorescence method. The expression of PGP 9.5 protein was used to assess the quantity and mean length as well as average and total fluorescence intensity of nerve fibers. Results. An increased expression of amphiregulin and nerve growth factor as well as increase in the quantity, mean length and average and total fluorescence intensity of nerve fibers were revealed in the epidermis of psoriatic patients. Following a course of the PUVA therapy, a decrease in the PASI index and extent of itching, reduced expression of amphiregulin and nerve growth factor as well as reduced quantity, mean length and average and total fluorescence intensity of nerve fibers in the epidermis were observed. Direct correlation dependence between the extent of itching, amphiregulin and nerve growth factor expression level and quantity and length of nerve fibers in the epidermis was discovered. Direct correlation dependence between the amphiregulin and nerve growth factor expression level, and average length of nerve fibers in the epidermis was discovered. Conclusion. The itching intensity in psoriatic patients receiving the PUVA therapy is reduced due to the decreased skin expression of the nerve growth factor and amphiregulin.

Ethanol Extract of Peanut Sprout Exhibits a Potent Anti-Inflammatory Activity in Both an Oxazolone-Induced Contact Dermatitis Mouse Model and Compound 48/80-Treated HaCaT Cells

Background

We developed an ethanol extract of peanut sprouts (EPS), a peanut sprout-derived natural product, which contains a high level of trans-resveratrol (176.75 µg/ml) and was shown to have potent antioxidant activity.

Objective

We evaluated the potential anti-inflammatory activity of EPS by measuring its antioxidant potential in skin.

Methods

The anti-inflammatory activity of EPS was tested using two models of skin inflammation: oxazolone (OX)-induced contact dermatitis in mice and compound 48/80-treated HaCaT cells. As biomarkers of skin inflammation, cyclooxygenase-2 (COX-2) and nerve growth factor (NGF) levels were measured.

Results

OX-induced contact dermatitis was suppressed markedly in mice that were treated with an ointment containing 5% EPS as evidenced by a decrease in the extent of scaling and thickening (p<0.05) and supported by a histological study. COX-2 (messenger RNA [mRNA] and protein) and NGF (mRNA) levels, which were upregulated in the skin of OX-treated mice, were suppressed markedly in the skin of OX+EPS-treated mice. Consistent with this, compound 48/80-induced expression of COX-2 (mRNA and protein) and NGF (mRNA) in HaCaT cells were suppressed by EPS treatment in a dose-dependent manner. As an inhibitor of NF-κB, IκB protein levels were dose-dependently upregulated by EPS. Fluorescence-activated cell sorting (FACS) analysis revealed that EPS scavenged compound 48/80-induced reactive oxygen species (ROS) in HaCaT cells.

Conclusion

EPS exerts a potent anti-inflammatory activity via its anti-oxidant activity in both mouse skin and compound 48/80-treated HaCaT cells in vitro. Compound 48/80-treated HaCaT cells are a useful new in vitro model of skin inflammation.

TRP channels in skin: from physiological implications to clinical significances

TRP channels are expressed in various cells in skin. As an organ system to border the host and environment, many nonneuronal cells, including epidermal keratinocytes and melanocytes, express several TRP channels functionally distinct from sensory processing. TRPV1 and TRPV3 in keratinocytes of the epidermis and hair apparatus inhibit proliferation, induce terminal differentiation, induce apoptosis, and promote inflammation. Activation of TRPV4, 6, and TRPA1 promotes regeneration of the severed skin barriers. TRPA1 also enhances responses in contact hypersensitivity. TRPCs in keratinocytes regulate epidermal differentiation. In human diseases with pertubered epidermal differentiation, the expression of TRPCs are altered. TRPMs, which contribute to melanin production in melanocytes, serve as significant prognosis markers in patients with metastatic melanoma. In summary, not only act in sensory processing, TRP channels also contribute to epidermal differentiation, proliferation, barrier integration, skin regeneration, and immune responses. In diseases with aberrant TRP channels, TRP channels might be good therapeutic targets.

Inflammation and itching in patients suffering from atopic dermatitis and psoriasis. Assessment of the expression of neurotrophins аnd neuropeptides

Goal. To assess the expression of neurotrophin, a nerve growth factor, amphiregulin, an epidermal growth factor, semaphorin 3A, a nerve repulsion factor, and PGP9.5 protein, a nerve fiber marker, in the skin of patients suffering from atopic dermatitis and psoriasis. Materials and methods. The study involved 30 patients suffering from atopic dermatitis and 30 patients suffering from psoriasis vulgaris. The disease severity was assessed by SCORAD and PASI. The extent of itching was assessed by the visual analogue scale. The expression of amphiregulin, semaphorin 3A (a nerve growth factor) and PGP9.5 protein (a nerve fiber marker) in the skin of patients was assessed by the indirect immunofluorescence method. Quantitative parameters of their expression were assessed by using the basic pack of the Olympus Fluoview software, Ver. 1.7b. Results. Increased epidermal innervation was revealed in the patients suffering from atopic dermatitis and psoriasis, which demonstrates an increased skin production of anti-inflammatory neuropeptides and reduced itching sensitivity threshold. A positive correlation between the itching extent and skin expression of neurotrophin (a nerve growth factor) was revealed in the patients with atopic dermatitis. In patients with severe psoriasis, an increased skin expression of amphiregulin, an epidermal growth factor, was discovered. Conclusion. These data demonstrate a pathogenic value of neurotrophin, a nerve growth factor, for the development of itching in patients with atopic dermatitis and amphiregulin in case of psoriasis vulgaris.

Neurotrophins and neuropeptides as inflammatory mediators in case of chronic dermatosis

This literature review examines the role of neurotrophins and neuropeptides for the development of skin inflammatory reactions in case of chronic inflammatory dermatoses. The article describes inflammatory effects of neurotrophin, a nerve growth factor, neuropeptide substance P and calcitonin gene-related peptide. Factors affecting the condition of skin innervation and development of inflammation - neurotrophin, a nerve growth factor, amphiregulin, an epidermal growth factor, and semaphorin 3A, a nerve repulsion factor - were examined. Searching for and administering antagonists of proinflammatory effects of neuropeptides, neurotrophins and epidermal growth factor can become new approaches to the treatment of chronic inflammatory dermatoses.

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

Epidermal hyperinnervation, which is thought to underlie intractable pruritus, has been observed in patients with atopic dermatitis (AD). The epidermal expression of axonal guidance molecules has been reported to regulate epidermal hyperinnervation. Previously, we showed that the excimer lamp has antihyperinnervative effects in nonpruritic dry-skin model mice, although epidermal expression of axonal guidance molecules was unchanged. Therefore, we investigated the antipruritic effects of excimer lamp irradiation and its mechanism of action. A single irradiation of AD model mice significantly inhibited itch-related behavior 1 day later, following improvement in the dermatitis score. In addition, irradiation of nerve fibers formed by cultured dorsal root ganglion neurons increased bleb formation and decreased nerve fiber expression of nicotinamide mononucleotide adenylyl transferase 2, suggesting degenerative changes in these fibers. We also analyzed whether attaching a cutoff excimer filter (COF) to the lamp, thus decreasing cytotoxic wavelengths, altered hyperinnervation and the production of cyclobutane pyrimidine dimer (CPD), a DNA damage marker, in dry-skin model mice. Irradiation with COF decreased CPD production in keratinocytes, as well as having an antihyperinnervative effect, indicating that the antipruritic effects of excimer lamp irradiation with COF are due to induction of epidermal nerve degeneration and reduced DNA damage.

Effects of magnesium deficiency--more than skin deep

Dead Sea and magnesium salt therapy are two of the oldest forms of treatment for skin disease and several other disorders, supported by a body of largely anecdotal evidence. In this paper we review possible pathways for penetration of magnesium ions through the epidermis to reach the circulation, in turn replenishing cellular magnesium levels. We also discuss mechanisms for intercellular movement of magnesium ions and possible mechanisms for the interaction between magnesium ions and inflammatory mediators. Upon addition of magnesium ions in vitro, the expression of inflammatory mediators such as tumour necrosis factor α (TNFα) and nuclear factor κβ (NFκβ) is down regulated. Dysregulation of these and other inflammatory mediators has been linked to several inflammatory disorders, including asthma, arthritis, atherosclerosis and neuroinflammation.