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![Dose-response curves for itch induction by intracutaneous injection of a PAR-2 agonist [tethered ligand; 50 l; 13 controls (open circles) and 14 AD patients (filled diamonds, lesional skin; filled circles, nonlesional skin)] and the reverse peptide (VKGILS-NH 2 ; 6 controls and 4 AD patients) are shown. Intensity of itch sensation after the injection was assessed on a scale from 0 to 10 at 10 sec intervals for 5 min. auc, Area under the curve; mean SEM.](profile/Martin-Steinhoff/publication/324509665/figure/fig2/AS:615128349278208@1523669435079/Dose-response-curves-for-itch-induction-by-intracutaneous-injection-of-a-PAR-2-agonist.png)
Dose-response curves for itch induction by intracutaneous injection of a PAR-2 agonist [tethered ligand; 50 l; 13 controls (open circles) and 14 AD patients (filled diamonds, lesional skin; filled circles, nonlesional skin)] and the reverse peptide (VKGILS-NH 2 ; 6 controls and 4 AD patients) are shown. Intensity of itch sensation after the injection was assessed on a scale from 0 to 10 at 10 sec intervals for 5 min. auc, Area under the curve; mean SEM.
Source publication
We examined whether neuronal proteinase-activated receptor-2 (PAR-2) may be involved in pruritus of human skin. The endogenous PAR-2 agonist tryptase was increased up to fourfold in atopic dermatitis (AD) patients. PAR-2 was markedly enhanced on primary afferent nerve fibers in skin biopsies of AD patients. Intracutaneous injection of endogenous PA...
Contexts in source publication
Context 1
... injection of the endogenous PAR-2 agonist SLIGKV dose-dependently provoked pain upon injection, and this pain was followed by an itch sensation lasting for 2-5 min. Cumulative itch ratings were higher for injections in nonlesional skin of AD patients for 1 and 5 mM tethered ligand, but this difference did not reach statistical significance ( p 0.15; ANOVA; planned comparison). However, when applied inside the eczema, SLIGKV provoked enhanced itch in the patients compared with that of control ( p 0.05; ANOVA; Scheffé post hoc). At higher concentrations, the reversed peptide VKGILS also provoked an itch response (Fig. 3, right). However, at a concen- tration of 0.5 mM, only the active agonist SLIGKV induced an itch response, when applied in the eczema. Figure 2. Double immunofluorescence staining of PAR-2 (B5 antiserum) and mast cell tryptase in lesional and nonlesional human skin biopsies of patients with AD. a, In lesional skin of patients with atopic dermatitis, staining for PAR-2 (red) can be observed in keratinocytes, blood vessels, certain inflammatory cells, and nerve-fiber-like structures. Mast cells (green) associated with PAR-2-positive blood vessels (100). b, Omission of antibodies against PAR-2 demonstrates only staining of mast cells by tryptase (100). c, Higher magnification reveals staining of small nerve fibers (arrow) in the dermis associated with blood vessels (red) and mast cells (green) (400). d, In lesional skin of patients with AD, increased staining for PAR-2 was observed in nerve fibers (arrows) closely associated with mast cells (green) (630) at higher magnification. e, Staining for PAR-2 (arrows) was also observed in nerve fibers of nonlesional skin from patients with AD (630). f, Control staining using the appropriate peptide for preabsorption (B5 antiserum) did not result in any PAR-2-like or tryptase-like immunoreactivity in either human skin tissue ...
Context 2
... ligand, but this difference did not reach statistical significance ( p 0.15; ANOVA; planned comparison). However, when applied inside the eczema, SLIGKV provoked enhanced itch in the patients compared with that of control ( p 0.05; ANOVA; Scheffé post hoc). At higher concentrations, the reversed peptide VKGILS also provoked an itch response (Fig. 3, right). However, at a concen- tration of 0.5 mM, only the active agonist SLIGKV induced an itch response, when applied in the eczema. Figure 2. Double immunofluorescence staining of PAR-2 (B5 antiserum) and mast cell tryptase in lesional and nonlesional human skin biopsies of patients with AD. a, In lesional skin of patients with atopic ...
Citations
... Antihistamine therapeutics targeting histamine receptor 1 provide relief of pruritus [16]. However, nonhistamine-dependent polymodal C-fibers would be activated in the epidermis with further activating protease-activated receptor 2 in the peripheral terminal [17]. The stimuli by pruritogen or noxious agents transmit the signal by spinothalamic tract neurons and further format the pruriceptive sensation [18], and therefore antihistamine agents provide insufficient efficacy for subjects with impaired somatosensory sensation [19]. ...
Background and hypothesis:
Pruritus is a common and distressing symptom that affects patients with chronic kidney disease. The concentration of protein bounded uremic toxin was associated with the uremic pruritus. The aim is to assess the efficacy of AST-120 for uremic pruritus in hemodialysis patients.
Materials and methods:
The participants were enrolled and then divided into the AST-120 treatment group and control group with a ratio of 2:1. All participants underwent pre-observation screenings two weeks before the study with three visits. In the treatment phase (week 1 to week 4), the treatment group added 6g/day of AST-120 along with routine anti-pruritic treatment. Visual analog scale (VAS) and biochemical parameters were measured.
Results:
The VAS score began to be lower in the AST-120 treatment group after the 5th visiting (p < 0.05). The reduction in indoxyl sulfate (IS) at 5th week along with TNF-alpha. The reduction ratio of indoxyl sulfate correlated with reduction of parathyroid hormone.
Conclusion:
This study has demonstrated that the four-week treatment of AST-120 decreased the severity of uremic pruritus in patients with ESRD. The concentration of IS and TNF-alpha decreased in the AST-120 treatment group. The reduction of iPTH correlated with the reduction of IS in the AST-120 treatment.
... Among TLRs, TLR3, TLR4, TLR5, and TLR7 have been known to mediate itch in mice [41,42]. Protease-activated receptors (PARs), especially PAR2 and PAR4, have been implicated in itch initiation by detecting various exogenous and endogenous proteases [43][44][45]. They are expressed by keratinocytes, immune cells, and neurons [46]. ...
Chronic itch is a debilitating condition with limited treatment options, severely affecting quality of life. The identification of pruriceptors has sparked a growing interest in the therapeutic potential of TRP channels in the context of itch. In this regard, we provided a comprehensive overview of the site-specific expression of TRP channels and their associated functions in response to a range of pruritogens. Although several potent antipruritic compounds that target specific TRP channels have been developed and have demonstrated efficacy in various chronic itch conditions through experimental means, a more thorough understanding of the potential for adverse effects or interactions with other TRP channels or GPCRs is necessary to develop novel and selective therapeutics that target TRP channels for treating chronic itch. This review focuses on the mechanism of itch associated with TRP channels at specific sites, from the skin to the sensory neuron, with the aim of suggesting specific therapeutic targets for treating this condition.
... However, when overabundant and/or aberrantly controlled, skin MCs contribute to a host of chronic inflammatory dermatoses, including atopic and contact dermatitis, psoriasis, prurigo, rosacea, urticaria, and mast cell activation syndrome [6,[32][33][34][35][36][37][38][39][40][41]. Through the formation of operating units with sensory neurons, skin MCs initiate not only inflammatory circuits but also the sensation of itch [42][43][44][45][46][47][48][49]. Itch is also a common symptom of chronic skin diseases, including atopic dermatitis. ...
Skin mast cells (MCs) are critical effector cells in acute allergic reactions, and they contribute to chronic dermatoses like urticaria and atopic and contact dermatitis. KIT represents the cells‘ crucial receptor tyrosine kinase, which orchestrates proliferation, survival, and functional programs throughout the lifespan. cAMP response element binding protein (CREB), an evolutionarily well-conserved transcription factor (TF), regulates multiple cellular programs, but its function in MCs is poorly understood. We recently reported that CREB is an effector of the SCF (Stem Cell Factor)/KIT axis. Here, we ask whether CREB may also act upstream of KIT to orchestrate its functioning. Primary human MCs were isolated from skin and cultured in SCF+IL-4 (Interleukin-4). Pharmacological inhibition (666-15) and RNA interference served to manipulate CREB function. We studied KIT expression using flow cytometry and RT-qPCR, KIT-mediated signaling using immunoblotting, and cell survival using scatterplot and caspase-3 activity. The proliferation and cycle phases were quantified following BrdU incorporation. Transient CREB perturbation resulted in reduced KIT expression. Conversely, microphthalmia transcription factor (MITF) was unnecessary for KIT maintenance. KIT attenuation secondary to CREB was associated with heavily impaired KIT functional outputs, like anti-apoptosis and cell cycle progression. Likewise, KIT-elicited phosphorylation of ERK1/2 (Extracellular Signal-Regulated Kinase 1/2), AKT, and STAT5 (Signal Transducer and Activator of Transcription) was substantially diminished upon CREB inhibition. Surprisingly, the longer-term interference of CREB led to complete cell elimination, in a way surpassing KIT inhibition. Collectively, we reveal CREB as non-redundant in MCs, with its absence being incompatible with skin MCs’ existence. Since SCF/KIT regulates CREB activity and, vice versa, CREB is required for KIT function, a positive feedforward loop between these elements dictates skin MCs’ fate.
... Skin barrier changes can also induce symptoms, which may be alleviated by corrections in pH. Serine proteases, which have increased function at an elevated pH, induce pruritus via PAR-2 receptor activation in keratinocytes and nerves in atopic skin [138]. Moreover, studies on hapten-induced atopic dermatitis in at-risk mice show that lowering the pH reduces the Th2 inflammatory response, prevents epidermal hyperplasia, reduces tissue eosinophilia, and normalizes the epidermal structure [13]. ...
An intact barrier function of the skin is important in maintaining skin health. The regulation of the skin barrier depends on a multitude of molecular and immunological signaling pathways. By examining the regulation of a healthy skin barrier, including maintenance of the acid mantle and appropriate levels of ceramides, dermatologists can better formulate solutions to address issues that are related to a disrupted skin barrier. Conversely, by understanding specific skin barrier disruptions that are associated with specific conditions, such as atopic dermatitis or psoriasis, the development of new compounds could target signaling pathways to provide more effective relief for patients. We aim to review key factors mediating skin barrier regulation and inflammation, including skin acidity, interleukins, nuclear factor kappa B, and sirtuin 3. Furthermore, we will discuss current and emerging treatment options for skin barrier conditions.
... TRPV1 is a crucial molecule in pruritus signaling in AD, as it is upregulated in AD lesions and its activation leads to the release of mediators that promote in ammation and itching (Steinhoff et al., 2003). Additionally, TRPV1 plays a role in maintaining epidermal barrier homeostasis. ...
Atopic dermatitis (AD) is a prevalent skin ailment in Asia, and the currently available clinical interventions provide only limited respite while potentially leading to undesired or severe side effects. This investigation explores ferulic acid's potential as an innovative and efficacious remedy for AD. Ferulic acid, recognized for its diverse pharmacological and biological attributes, underwent evaluation through both cellular and in vivo studies. The outcomes revealed that ferulic acid adeptly mitigated the inflammatory retort associated with AD by quelling the activation of the TRPV1 and HMGB1 signaling pathways—both tied to the Transient Receptor Potential Cation Channel, Subfamily V, Member 1 (TRPV1) and High Mobility Group Protein 1 (HMGB1). In a BALB/c mouse model, ferulic acid demonstrated significant amelioration of AD symptoms prompted by DNCB, including the reduction of skin barrier impairment, diminished ear and skin epidermal thickness, curbed mast cell infiltration, and decreased spleen and lymph node dimensions. These findings underscore the potential of ferulic acid as a viable treatment avenue for AD. The multifaceted attributes of ferulic acid, its confirmed pharmacological and biological merits, and its demonstrated effectiveness in assuaging AD's inflammatory responses, as validated by cellular and in vivo investigations, collectively propose its significant promise as a compelling substitute in the therapeutic landscape for AD.
Running head: Ferulic acid inhibits inflammation in AD
... Highly selective activation of MCs induces itch in mice via LTC 4 , serotonin, and S1p [53]. Additionally, MCs are known to release other pro-pruritic substances such as tryptase [54], lipid mediators (prostaglandins, phospholipase A2, LTB 4 ) [55][56][57], and cytokines (IL-4, IL-13, IL-25 and IL-31) [58-61], though the specific contribution of MCs in the overall pruritic context is not well defined. ...
... Cathepsin B localises to the secretory granules of primary human skin-derived MCs, and is required for the activation of protryptase into active tryptase [119]. MCs have been suggested to contribute to psoriatic pruritus by releasing tryptase [54,120]. Because human tryptase is a PAR-2 ligand, the significant upregulation of CTSB in MCs in psoriasis lesions and the correlation of cathepsin B with PASI would suggest a contribution to promoting PAR-2 signalling in sensory nerve fibres. ...
Mast cells (MCs) contribute to skin inflammation. In psoriasis, the activation of cutaneous neuroimmune networks commonly leads to itch. To dissect the unique contribution of MCs to the cutaneous neuroinflammatory response in psoriasis, we examined their density, distribution, relation to nerve fibres and disease severity, and molecular signature by comparing RNA-seq analysis of MCs isolated from the skin of psoriasis patients and healthy volunteers. In involved psoriasis skin, MCs and Calcitonin Gene-Related Peptide (CGRP)-positive nerve fibres were spatially associated, and the increase of both MC and nerve fibre density correlated with disease severity. Gene set enrichment analysis of differentially expressed genes in involved psoriasis skin showed significant representation of neuron-related pathways (i.e., regulation of neuron projection along with dendrite and dendritic spine morphogenesis), indicating MC engagement in neuronal development and supporting the evidence of close MC–nerve fibre interaction. Furthermore, the analysis of 208 identified itch-associated genes revealed that CTSB, TLR4, and TACR1 were upregulated in MCs in involved skin. In both whole-skin published datasets and isolated MCs, CTSB was found to be a reliable indicator of the psoriasis condition. Furthermore, cathepsin B+ cells were increased in psoriasis skin and cathepsin B+ MC density correlated with disease severity. Therefore, our study provides evidence that cathepsin B could serve as a common indicator of the MC-dependent itch signature in psoriasis.
... For example, serum tryptase levels were increased in renal disease with pruritus, and the intensity of pruritus correlated significantly with tryptase levels [197]. Tryptase level were also increased in AD patients with moderate to severe pruritus [198]. The connection of tryptase and pruritus is further supported by the correlation of blood tryptase reduction in AD patients treated with fexofenadine, an antihistamine, with pruritus improvement [199] (Fig. 3) Enhanced levels of tryptase release and tryptase activity are related to itch in chronic dermatitis, P-phenylenediamine-induced itch, and ovalbumin allergyinduced itch in mice [200][201][202]. ...
... PAR-2 is involved in the pathophysiology of many inflammatory diseases, including AD. In the skin of patients with AD, the number of PAR-2 positive nerve fibers is significantly increased, and intracutaneous injection of endogenous PAR-2 agonists causes enhanced and prolonged itch [198]. Interestingly, skin of patients with AD has been found to be presensitized for protease-induced itch [257]. ...
Primary cutaneous T-cell lymphomas (CTCL), which include mycosis fungoides (MF) and Sézary syndrome (SS), are a group of lymphoproliferative disorders characterized by clonal accumulation of neoplastic T-lymphocytes in the skin. Severe pruritus, one of the most common and distressing symptoms in primary CTCL, can significantly impair emotional well-being, physical functioning, and interpersonal relationships, thus greatly reducing quality of life. Unfortunately, effectively managing pruritus remains challenging in CTCL patients as the underlying mechanisms are, as of yet, not fully understood. Previous studies investigating the mechanisms of itch in CTCL have identified several mediators and their corresponding antagonists used for treatment. However, a comprehensive overview of the mediators and receptors contributing to pruritus in primary CTCL is lacking in the current literature. Here, we summarize and review the mediators and receptors that may contribute to pruritus in primary CTCL to explore the mechanisms of CTCL pruritus and identify effective therapeutic targets using the PubMed and
... In the study of Steinhoff et al., PAR-2 was significantly enhanced on skin biopsies of 38 patients with AD. On the other hand, tryptase (endogenous PAR-2 agonist) was increased up to fourfold [177]. Nishimoto et al. also demonstrated the crosstalk between PAR-2-and IL-4-mediated inflammatory axes, hence being a potential platform for mechanism-targeted drugs [176]. ...
Atopic dermatitis represents a complex and multidimensional interaction that represents potential fields of preventive and therapeutic management. In addition to the treatment armamentarium available for atopic dermatitis, novel drugs targeting significant molecular pathways in atopic dermatitis biologics and small molecules are also being developed given the condition’s complex pathophysiology. While most of the patients are expecting better efficacy and long-term control, the response to these drugs would still depend on numerous factors such as complex genotype, diverse environmental triggers and microbiome-derived signals, and, most importantly, dynamic immune responses. This review article highlights the challenges and the recently developed pharmacological agents in atopic dermatitis based on the molecular pathogenesis of this condition, creating a specific therapeutic approach toward a more personalized medicine.
... Sensory neurons expressing Mrgprs also regulate histamineindependent pruritus (Wilson et al., 2011). Due to the critical role of various proteases, TRPs, and Mrgprs in skin homeostasis and the pathophysiology of pruritus (Rajka, 1967;Steinhoff et al., 2003;Reddy et al., 2015;Coavoy-Sánchez et al., 2016), the co-participation of these receptors in the anti-pruriceptive effects of SGE was assessed. CQ is commonly used to prevent or treat malaria, but, as a side effect, produces intense itching in humans (Sowunmi et al., 1989;Sowunmi et al., 2001) or in mice when i.d. ...
Aedes aegypti ( Ae. aegypti ) saliva induces a variety of anti-inflammatory and immunomodulatory activities. Interestingly, although it is known that mosquito bites cause allergic reactions in sensitised hosts, the primary exposure of humans to Ae. aegypti does not evoke significant itching. Whether active components in the saliva of Ae. aegypti can counteract the normal itch reaction to injury produced by a histaminergic or non-histaminergic pathway in vertebrate hosts is unknown. This study investigated the effects of Ae. aegypti mosquito salivary gland extract (SGE) on sensitive reactions such as itching and associated skin inflammation. Acute pruritus and plasma extravasation were induced in mice by the intradermal injection of either compound 48/80 (C48/80), the Mas-related G protein-coupled receptor (Mrgpr) agonist chloroquine (CQ), or the transient receptor potential ankyrin 1 (TRPA1) agonist allyl isothiocyanate (AITC). The i.d. co-injection of Ae. aegypti SGE inhibited itching, plasma extravasation, and neutrophil influx evoked by C48/80, but it did not significantly affect mast cell degranulation in situ or in vitro . Additionally, SGE partially reduced CQ- and AITC-induced pruritus in vivo , suggesting that SGE affects pruriceptive nerve firing independently of the histaminergic pathway. Activation of TRPA1 significantly increased intracellular Ca ²⁺ in TRPA-1-transfected HEK293t lineage, which was attenuated by SGE addition. We showed for the first time that Ae. aegypti SGE exerts anti-pruriceptive effects, which are partially regulated by the histamine-independent itch TRPA1 pathway. Thus, SGE may possess bioactive molecules with therapeutic potential for treating nonhistaminergic itch.
... Proteinase-activated receptor-2 (PAR-2) was first associated with a novel non-histaminergic pruritic pathway in research performed on patients suffering from atopic dermatitis (AD). Steinhoff et al. revealed not only an enhanced level of this receptor in skin biopsies of AD patients but also proved itch sensations appearing after intracutaneous injection of endogenous PAR-2 agonist [37]. Subsequently, a pilot study conducted on 12 ESRD patients with pruritus, four ESRD patients without pruritus, and six healthy controls documented higher serine protease activity in skin samples taken from pruritic patients. ...
Recent studies place great importance on Protein-Bound Uraemic Toxins (PBUT) in the context of etiopathogenesis of chronic kidney disease-associated pruritus (CKD-aP). This study aimed to investigate the possible contribution of free and total Indoxyl Sulfate (IS) and p-Cresol Sulfate (PCS) to the cause of CKD-aP. Group A included 64 patients on maintenance haemodialysis (HD) with CKD-aP. Group B included 62 patients on maintenance HD that did not report CKD-aP, and group C included 50 healthy controls. Pruritus severity was assessed using a Numerical Rating Scale (NRS). Moreover, other tools like UP-Dial, ItchyQoL, and the 4-Item Itch Questionnaire evaluating CKD-aP were completed by the patients. The serum levels of free and total IS and PCS concentrations were measured using the Ultra Performance Liquid Chromatography System. No significant difference in the serum level of free and total IS, or PCS, was observed between the patients who reported CKD-aP and those without pruritus. Moreover, there was no correlation between serum IS or PCS levels and the severity of the itch. Our study does not support earlier findings about higher levels of IS and PCS in patients reporting CKD-aP. Further studies will be needed to investigate these discrepancies as well as to understand the cause of CKD-aP.
