Cutaneous Mast Cells Research Articles

CD25 Expression on Cutaneous Mast Cells From Adult Patients Presenting With Urticaria Pigmentosa is Predictive of Systemic Mastocytosis

Urticaria pigmentosa (UP) is a clinicopathologic term used to describe reddish-brown cutaneous macules and papules, characterized histologically by mast cell infiltration of the papillary and upper reticular dermis and reactive basal hyperpigmentation of the overlying epidermis. Although typically a benign, self-limited disorder of childhood, a significant proportion (up to 30%) of adolescent and adult-onset UP represents cutaneous involvement by underlying systemic mastocytosis (SM). Predicting the course of cutaneous mast cell disease has been limited by a lack of diagnostic and prognostic markers. In patients with SM, neoplastic bone marrow mast cells show aberrant surface expression of CD25. However, whether CD25 expression on cutaneous mast cells is associated with underlying SM is unknown. In this study, we performed a clinicopathologic analysis of 30 adult patients presenting with UP between 1987 and 2007. Cutaneous mast cell infiltration pattern, cytomorphology, density, and CD25 immunoreactivity were correlated with underlying or subsequent SM. On the basis of clinical and pathologic follow-up, 10 of 30 (33%) patients were diagnosed with SM and 20 of 30 (67%) with limited cutaneous mastocytosis (CM). Although cutaneous mast cell density was slightly higher in patients with SM compared to those with limited CM (P=0.047), neither mast cell cytomorphology nor infiltration pattern correlated with underlying systemic disease. However, cutaneous mast cells from all 10 patients with SM (100%) were immunoreactive for CD25, compared to only 5 of 20 (25%) with limited CM (P<0.001). Our findings suggest that immunoreactivity for CD25 in cutaneous mast cells may be useful for stratifying adult patients presenting with UP for additional clinical evaluation.

Cutaneous mononuclear cells and eosinophils are significantly increased after warm water challenge in pruritic areas of polycythemia vera

Increased cutaneous cells following warm water challenge in pruritus-related polycythemia vera (PV) have been reported, but their nature and magnitude are not known. Qualitative and quantitative assessments (digital image analysis) of the cutaneous mononuclear cells, eosinophils and mast cells were carried out in PV patients and healthy controls (n = 10 each) following exposures to water at room temperature and warm water. Infiltration of the spongiotic epidermis and dermis by mononuclear cells and eosinophils together with edema and vasodilatation of upper dermis following warm water contact was clearly observed only in PV patients. In contrast to controls, significant increase in numbers of mononuclear cells and eosinophils in comparison with exposure to water at room temperature at the dermal-epidermal junction (p < 0.01), papillary dermis (p < 0.01) and perivascular area (p < 0.05) was found. Obvious mast cell degranulation was seen in PV sections after warm water contact, but no significant increase of their numbers was observed whether among PV patients or healthy controls (p > 0.05). However, the numbers of papillary dermal mast cells in specimens obtained from PV patients following room temperature water exposure were significantly more than those of healthy controls (p < 0.05). PV represents an invisible dermatosis in which the infiltrating mononuclear cells and eosinophils may have a role in warm water-induced pruritus.

Control of Pseudomonas aeruginosa Skin Infections in Mice Is Mast Cell-Dependent

Mast cells (MCs) have recently been shown to be essential for the elicitation of efficient immune responses in murine sepsis. To explore whether MCs also contribute to the control of bacterial skin infections, we studied skin lesions induced by Pseudomonas aeruginosa (PA) in genetically MC-deficient Kit(W)/Kit(W-v) mice, normal Kit(+/+) mice, and MC-reconstituted Kit(W)/Kit(W-v) mice. PA injections resulted in strikingly (>2-fold) larger skin lesions in Kit(W)/Kit(W-v) mice than in Kit(+/+) mice, which exhibited pronounced MC degranulation at infection sites. In addition, neutrophil recruitment following PA injections and bacterial clearance from sites of infection was significantly impaired in Kit(W)/Kit(W-v) mice compared with Kit(+/+) mice. Notably, the adoptive transfer of MCs to the skin of Kit(W)/Kit(W-v) mice before PA infection resulted in normal neutrophil accumulation as well as skin lesions comparable with those in Kit(+/+) mice in both bacterial burden and size. These findings demonstrate for the first time that activated MCs are crucial for the induction of protective innate immune responses to bacterial skin infections.

The effect of Na+-K+ ATPase inhibition by ouabain on histamine release from human cutaneous mast cells

There are controversial reports on the effect of sodium-potassium adenosine triphosphatase (Na+-K+ ATPase) inhibition on mast cell mediator release. Some of them have indicated that ouabain (strophanthin G), a specific Na+-K+ ATPase inhibitor, inhibited the release, whereas the others have shown that ouabain had no effect or even had a stimulatory effect on the mediator secretion. Most of these studies have utilized animal-derived mast cells. The aim of this study was to determine the effect of Na+-K+ ATPase inhibition on human skin mast cells. Unpurified and purified mast cells were obtained from newborn foreskins and stimulated by calcium ionophore A23187 (1 microM) for 30 min following a 1 hr incubation with various concentrations (10(-4) to 10(-8) M) of ouabain. Histamine release was assayed by enzyme-linked immunosorbent assay (ELISA). The results indicated that ouabain had no significant effect on the non-immunologic histamine release from human skin mast cells, in vitro. Na+-K+ ATPase inhibition by ouabain had no significant effect on the non-immunologic histamine release from human cutaneous mast cells and suggested differences between human and animal mast cells.

Role of proteinase‐activated receptors (PARs) during cutaneous inflammation and the immune response

Proteinase‐activated receptors constitute a new subfamily of G protein‐coupled receptors with seven transmembrane domains which are activated by various exogenous or endogenous serine proteinases such as thrombin, cathepsin G, trypsins, tryptase, clotting factors (VV, Xa), bacterial proteases or mite antigens. In addition, PAR1 can be activated by MMP‐1. Recent knowledge indicate that proteases are not merely enzymes which cleave proteins in the extracellular space, but are signaling molecules involved in many processes by activating specific receptors in an autocrine, paracrine and endocrine fashion. MMP‐1 activates PAR1 and is thereby involved in the migration and invasive potential of melanoma cells. PAR2 is a receptor for mast cell tryptase or house dust mite allergens which is released during inflammation and allergic reactions. In the skin, PAR2 is diversly expressed by keratinocytes, endothelial cells and occasionally on sensory nerves of human skin in various disease states. Moreover, immunocompetent cells such as mast cells and neutrophils express functional PAR2 thereby contributing to inflammation and host defense. Own data revealed that PAR2 contributes to neurogenic inflammation by releasing neuropeptides from sensory nerves resulting in edema, plasma extravasation and infiltration of neutrophils. Thus, mast cells may communicate with sensory nerves in inflammatory tissues by activating PAR2 via tryptase. Vice versa, PAR2 activation of cutaneous mast cells leads to a release of histamine suggesting a bidirectional pathway of mast cell–nerve communication. Moreover, PAR2 agonists up‐regulate expression of certain cell adhesion molecules and cytokines such as interleukin‐6 and interleukin‐8 on dermal microvascular endothelial cells or regulate neutrophil migration or integrin expression – a role of PAR2 in leukocyte/endothelial interactions. These effects may be partly mediated by NF‐κB, an important transcription factor during inflammation and immune response. PAR2 stimulation results in the activation of NF‐κB on microvascular endothelial cells and keratinocytes thereby regulating ICAM‐1 expression. We also demonstrate evidence for a diverse expression of PAR2 in various skin diseases and highlight the recent knowledge about the important role of PAR2 during inflammation and the immune response. Together, PAR2‐modulating agents may be new tools for the treatment of inflammatory and allergic diseases in the skin.

Anti‐CXCR3 staining is useful for detecting human cutaneous and mucosal mast cells

Human synovial mast cells (MC) can be immunolabelled with antihuman CXCR3 antibody (Ab) (clone 49801). We have investigated whether cutaneous and mucosal MC are stained with anti-CXCR3 Ab in paraffin-embedded sections. Immunohistochemical staining and immunofluorescence double staining assays were performed with anti-CXCR3, anti-tryptase, and anti-chymase Ab using normal skin, psoriatic skin lesions, and normal colon. When compared with tryptase and chymase staining, 100% of the cutaneous and 98% of the mucosal MC were positive for CXCR3. Anti-CXCR3 staining is a useful marker for human cutaneous and mucosal MC in paraffin-embedded sections.

Functional Characterization and Expression Analysis of the Proteinase-Activated Receptor-2 in Human Cutaneous Mast Cells

Proteinase-activated receptor-2 (PAR2) belongs to a new G protein-coupled receptor subfamily activated by serine proteinases. PAR2 has been demonstrated to play a role during inflammation and immune response in different tissues including the skin. We examined whether PAR2 is functionally expressed by cutaneous human primary skin mast cells (HPMC) and the human mast cell line 1 (HMC-1). Reverse transcription-polymerase chain reaction and FACS analysis show expression of PAR2 both at the RNA and protein level. HPMCs and HMC-1 also express PAR1, PAR3, and PAR4. Ca-mobilization studies demonstrate functional PAR2 expressed by human skin mast cells, as shown by natural and synthetic PAR2 agonists. PAR2 agonists induced histamine release from HPMC indicating a role of PAR2 in regulating inflammatory and immune responses by skin mast cells. Double-immunofluorescence staining reveals colocalization of PAR2 with tryptase in the majority of human skin mast cells. In conclusion, trypsin and tryptase as well as specific agonists for PAR2 were able to induce Ca2+ mobilization in HPMCs, and agonists of PAR2 induce the release of histamine from these cells. Thus, PAR2 may be an important regulator of skin mast cell function during cutaneous inflammation and hypersensitivity.

The receptor for erythropoietin is present on cutaneous mast cells

Skin samples from patients with extra-mammary Paget disease, Bowen's disease, atopic dermatitis, psoriasis and non-lesional skin of nevus pigmentosus were immunohistochemically examined with an anti-soluble erythropoietin receptor antibody (anti-sEPOR antibody), and only the dermal mast cells positively stained in all skin samples were examined. These positively stained dermal cells were proved to be mast cells by double staining with anti-sEPOR antibody and either with anti-bikunin antibody or anti-tryptase antibody. Immunoelectron microscopically these EPOR were found in the secretory granules of the dermal mast cells. Further, EPOR in the mast cells may be consisting of only the extracellular domain of erythropoietin receptor molecule as the mast cells were immunohistochemically not reacted with an antibody to the C-terminal peptide of EPOR. Human mast cell line, HMC-1 cells has immunohistochemically the erythropoietin receptor, which was consisting of a 43 kDa major protein and a 20 kDa minor protein in the immunoelectrophoresis. These data may indicate that EPOR in the mast cells may not be the whole molecule, but probably the soluble one of EPOR.

Detection of basophil-activating IgG autoantibodies in chronic idiopathic urticaria by induction of CD63

Approximately 40% to 50% of patients with chronic idiopathic urticaria (CIU) have functional IgG autoantibodies against FcepsilonRIalpha or IgE, which induce histamine release from basophils and cutaneous mast cells. A positive autologous serum skin test response is believed to reflect the presence of these autoantibodies. We sought to further define the functional properties of and develop a sensitive functional assay for detection of autoantibodies in patients with CIU. Sera from patients with CIU (n=61) and sera from healthy control subjects (n=23) were incubated with donor basophils. Activation of basophils was determined on the basis of CD 63 surface expression, as analyzed on a FACScan flow cytometer. A positive basophil activation test result was found in 51% of patients with CIU, and basophil-activating properties were present in the IgG fractions of sera. When both the in vitro test and the autologous serum skin test were considered, basophil/mast cell-activating autoantibodies were present in 62% of the patients. Patients with a positive basophil activation test result had a significantly higher prevalence of other autoantibodies, had more severe urticaria, and were more likely to have angioedema. The results demonstrate the presence of basophil-activating autoantibodies in about 50% of patients with CIU. The data support the autoimmune cause of the disease and provide a simple test for detection of these autoantibodies.

The Influence of Long‐chain Polyunsaturated Fatty Acids on Total Lipid Fatty Acid Composition of a Canine Mastocytoma Cell Line

Cutaneous mast cells are considered as key immune effectors in the pathogenesis of canine atopic dermatitis (CAD). These cells release immediate-phase and late-phase mediators of inflammation. Dietary fatty acids are incorporated in cellular membranes and seem to influence mediator production and release. A dietary intervention with n6- and n3-fatty acids is thought to alleviate clinical symptoms in atopic dogs. The purpose of this study was to examine the effects of n6- and n3-fatty acids on the fatty acid composition of canine mastocytoma cells (C2) as a possible model for CAD. The C2 was cultured in a basic medium called Dulbecco's modified Eagle's medium (DEH) or with additional 14 mum linoleate (C18:2n6, DEH-LA), gamma-linolenate (C18:3n6, DEH-GLA), arachidonate (C20:4n6, DEH-AA), alpha-linolenate (C18:3n3, DEH-LnA), eicosapentaenoate (C20:5n3, DEH-EPA) or docosahexaenoate (C22:6n3, DEH-DHA). Cell growth was examined for 11 days in all media. Cell growth increased from days 1 to 8 and decreased thereafter in all media conditions. The fatty acids supplied did not influence cell growth. The cells were harvested after 8 days for fatty acid analysis. The fatty acid composition was determined by gas chromatography after extraction and trans-esterification of the lipids. The added fatty acids increased the concentration of these fatty acids in C2 differently (LA 4.9-fold, GLA 6.9-fold, AA 6-fold, LNA 9.3-fold, EPA 6.5-fold and DHA 8.4-fold). Furthermore, elongated and Delta6-desaturated products of the corresponding fatty acids were significantly elevated. However, Delta5-desaturated products were not measurable. These results let us assume that C2 has no measurable activity of the Delta5-desaturase. In case the low activity of Delta5-desaturase is one of the mechanisms underlying the pathogenesis of CAD, C2 seems to be an adequate model for investigations in CAD.

Functional assessment of pathogenic IgG subclasses in chronic autoimmune urticaria

Chronic urticaria is caused by a complement fixing, IgG antibody directed to the alpha-subunit of the IgE receptor, which is present in 35% to 45% of patients. This autoimmune subgroup can be identified by an autologous skin test or histamine release from human basophils or cutaneous mast cells. However, binding assays do not correlate with these functional assays. We considered the possibility that pathogenic antibody may be present within particular IgG subclasses, which might facilitate development of a binding method that can reliably screen patients. To determine the subclass distribution of IgG antireceptor antibodies on the basis of histamine release, and to assess the possibility that a subclass specific ELISA binding method could be used to screen patients. We isolated patient IgG by protein G affinity chromatography and then isolated patient IgG subclasses 1, 2, 3, and 4 by a combination of antibody affinity chromatography and protein A affinity chromatography. The ability of each subclass to activate basophils was assayed by histamine release. Patient IgG subclasses IgG 1 , IgG 3 , and to a lesser degree IgG 4 have antibody capable of activating basophils to release histamine, whereas IgG 2 is inactive. Immunoblot or RAST assay that is subclass-specific does not correlate with histamine release as a result of nonfunctional but binding antibody within IgG subclasses 1, 3, or 4, and complement activation by IgG 1 and IgG 3 . Purification of IgG subclasses from patients with chronic urticaria demonstrates functional antibody in IgG 1 and IgG 3 and occasionally IgG 4 . Nonfunctional antibody within IgG 2 plus nonfunctional antibody mixed with functional antibody within IgG 1 , IgG 3 , and IgG 4 and effects of complement are responsible for a lack of correlation of histamine release with binding assays even if subclass-specific.

Ultraviolet a photoprotection: Aging and cutaneous mast cells

Ultraviolet a photoprotection: Aging and cutaneous mast cells

Lack of significant skin inflammation during elimination by apoptosis of large numbers of mouse cutaneous mast cells after cessation of treatment with stem cell factor

We previously reported that subcutaneous (s.c.) administration of stem cell factor (SCF), the ligand for the c-Kit receptor, to the back skin of mice promotes marked local increases in the numbers of cutaneous mast cells (MCs), and that cessation of SCF treatment results in the rapid reduction of cutaneous MC populations by apoptosis. In the present study, we used the 125I-fibrin deposition assay, a very sensitive method for quantifying increased vascular permeability, to assess whether the clearance of large numbers of apoptotic MCs is associated with significant cutaneous inflammation. The s.c. injection of rrSCF164 (30 or 100 μg/kg/day) or rrSCF164-peg (polyethylene glycol-treated SCF, 30 or 100 μg/kg/day) for 23 days increased the numbers of dermal MCs at skin injection sites from 5.1±0.7 MCs/mm2 to 36.4±4.1, 34.7±9.7, 52.5±5.8, and 545±97 MCs/mm2, respectively. In contrast, MC numbers were markedly lower in mice that had been treated with SCF for 21 days, followed by 2 days of injection with the vehicle alone. Notably, when tested during the period of rapid reduction of skin MCs,125I-fibrin deposition in the skin was very similar to that in mice receiving continuous treatment with SCF or vehicle. We conclude that the rapid elimination of even very large populations of MCs by apoptosis, which also results in the clearance of the considerable quantities of proinflammatory products stored by these cells, does not lead to significant local cutaneous inflammatory responses.

Combined Mastocytoma-Junctional Nevus

A unique combined mastocytoma-junctional nevus presented as a 4-mm dark brown macule in the axilla of a 57-year-old white female. Histopathologic examination revealed a proliferation of mast cells partially or completely filling the dermal papillae, hyperpigmentation of the basal keratinocytes and mildly increased basal melanocytes. Overlying the mast cell proliferation, pigmented junctional nevus nests were present. The mast cells were strongly positive with Giemsa stain and mast cell tryptase immunohistochemical stain; nevomelanocytic cells were negative. Nevomelanocytes were strongly immunoreactive for S100, HMB-45, Mart-1, and tyrosinase; mast cells were negative. The clinicopathologic features suggested a synchronous proliferation of 2 cell types in the same small cutaneous field rather than a collision tumor. While the cutaneous mast cells probably originated as a disseminated clone, it is postulated that local mast cell growth factor induced nevomelanocytic proliferation and modulated mast cell growth. In fact, the tumor exhibited strong immunoreactivity for the mast cell growth factor receptor (CD117) in mast cells, basal melanocytes, and nevus nests. The incidence of dual mast cell-melanocytic tumors appears to be very low, as only 3 total cases have now been reported. However, since in patients with multiple mastocytomas only a small fraction of lesions are biopsied, the true incidence may be higher than supposed.

Chronic urticaria: Expanding the autoimmune kaleidoscope

Chronic urticaria: Expanding the autoimmune kaleidoscope

Synergistic regulation of neuropeptide levels by internal and external stimuli

The skin is the most peripheral organ confronting the external environment. We found that the level of substance P is regulated by both internal and external stimuli. Mock interview induced the acute stress in human assessed by the measurement of serum cortisol. The serum level of substance P increased within 1 h after the mock interview. Interestingly, the increase was suppressed by inhalation of 1,3‐dimethoxy‐5‐methylbenzene. Similar regulation was observed in mice. Furthermore, restraint or the intravenous administration of substance P induced the activation of cutaneous mast cells. Housing under the condition of lower humidity (about 30%) for 24 h caused the increase in the substance P level both in peripheral blood and in the skin. Restraint for 2 h during the housing under the condition of lower humidity increased the substance P level further. The activation of cutaneous mast cells under the dry condition was reported. These data suggest that cutaneous neuropeptide level is regulated by both psychological and environmental mechanisms. The regulation may cause the downregulation of the threshold of the induction of itch and inflammation.

Cholestatic pruritus - the role of cutaneous mast cells and nerves.

The pathogenesis of pruritus in cholestatic liver disease is poorly understood. Cutaneous mast cells and nerves are thought to contribute to pruritus in several dermatological diseases. To determine if cutaneous mast cell density, neural density and mast cell-neural interaction are increased in patients with pruritus and cholestatic liver disease. Skin biopsy specimens from (i). patients with pruritus due to cholestatic liver disease (CLDP+; n = 6), (ii). patients with chronic liver disease without pruritus (CLDP-; n = 5), and (iii). healthy controls (n = 6) were studied. Biopsies were dual stained immunohistochemically for mast cells and nerves. Mast cell density in the control group was not significantly different from that in CLDP+ group or from that in the CLDP- group. Similarly neural density was not significantly different between groups when assessed either in terms of total nerve area, or in terms of the number of neural elements seen. The frequency of mast cell-nerve contact was not significantly different between groups. These findings suggest that mast cells, nerves or interaction between the two may not contribute to cholestatic pruritus. Therefore, therapies targeted at cutaneous mast cells or nerves are unlikely to be of benefit.

The effect of cutaneous mast cell degranulation on sensitivity to heat.

To determine whether depletion of inflammatory mediators from cutaneous mast cells influences cutaneous sensitivity to heat or the thermal hyperalgesia provoked by capsaicin or noradrenaline. Ten healthy men. Compound 48/80 was introduced by iontophoresis into the forearm. Wheals at the site of compound 48/80 iontophoresis subsided over four pre-treatments, consistent with mast cell degranulation. Flares in the skin surrounding the compound 48/80 sites decreased after the first pre-treatment but persisted to some extent after wheals had disappeared, suggesting that a reagent produced during mast cell activation (e.g., a cytokine or lipoxygenase product released from degranulated mast cells) triggered a residual flare. Sensitivity to heat increased after the second administration of compound 48/80, possibly due to sensitization of thermal nociceptors by inflammatory mediators released from infiltrating leukocytes. However, the compound 48/80 pre-treatment inhibited the hyperalgesic effect of capsaicin. Pre-treatment with compound 48/80 did not prevent axon-reflex vasodilatation to noradrenaline or the hyperalgesic effect of noradrenaline in capsaicin-treated skin. Two mechanisms could account for the inhibitory effect of the compound 48/80 pre-treatment on the hyperalgesic effect of capsaicin. First, mast cell products could partly mediate the hyperalgesic effect of capsaicin. Second, partial desensitization of the vanilloid receptor subtype-1 by a reagent produced during mast cell activation (e.g., a lipoxygenase product) could mask the hyperalgesic effect of capsaicin. Mast cells do not appear to mediate the hyperalgesic effect of noradrenaline.

The vesicular monoamine transporter 2 (VMAT2) is expressed by normal and tumor cutaneous mast cells and Langerhans cells of the skin but is absent from Langerhans cell histiocytosis.

Monoamine storage in secretory granules is mediated by the vesicular monoamine transporters 1 and 2 (VMAT1 and VMAT2). The aim of our study was to identify monoamine-handling normal and neoplastic inflammatory cells in the skin by their expression of VMAT1 and VMAT2. Normal skin from various parts of the body, as well as 21 cases of cutaneous mastocytosis and 10 cases of cutaneous Langerhans cell histiocytosis were analyzed by immunohistochemistry, radioactive in situ hybridization, and double-fluorescence confocal microscopy. VMAT2-positive cells in the subepidermal layer were identified as mast cells by their expression of tryptase. Neoplastic mast cells in all cases of cutaneous mastocytosis retained their VMAT2 positivity. The intraepidermal VMAT2-expressing cells were identified as Langerhans cells by their CD1a positivity. VMAT2 was absent from Langerhans cell histiocytosis. VMAT2 is an excellent marker for normal and neoplastic mast cells. The expression of VMAT2 demonstrates the capacity of mast cells for monoamine storage and handling. The presence of VMAT2 in epidermal Langerhans cells revealed a previously unrecognized monoamine-handling phenotype of these cells and indicates possible involvement of amine storage and release associated with antigen presentation. Absence of VMAT2 in neoplastic Langerhans cells indicates a loss of monoamine handling capacity of these cells during tumorigenesis.

Expression of vanilloid receptor subtype 1 in cutaneous sensory nerve fibers, mast cells, and epithelial cells of appendage structures.

The vanilloid receptor subtype 1 (VR1)/(TRPV1), binding capsaicin, is a non-selective cation channel that recently has been shown in human keratinocytes in vitro and in vivo. However, a description of VR1 localization in other cutaneous compartments in particular cutaneous nerve fibers is still lacking. We therefore investigated VR1 immunoreactivity as well as mRNA and protein expression in a series (n = 26) of normal (n = 7), diseased (n = 13) [prurigo nodularis (PN) (n = 10), generalized pruritus (n = 1), and mastocytosis (n = 2)], and capsaicin-treated human skin (n = 6). VR1 immunoreactivity could be observed in cutaneous sensory nerve fibers, mast cells, epidermal keratinocytes, dermal blood vessels, the inner root sheet and the infundibulum of hair follicles, differentiated sebocytes, sweat gland ducts, and the secretory portion of eccrine sweat glands. Upon reverse transcriptase-polymerase chain reaction and Western blot analysis, VR1 was detected in mast cells and keratinocytes from human skin. In pruritic skin of PN, VR1 expression was highly increased in epidermal keratinocytes and nerve fibers, which was normalized after capsaicin application. During capsaicin therapy, a reduction of neuropeptides (substance P, calcitonin gene-related peptide) was observed. After cessation of capsaicin therapy, neuropeptides re-accumulated in skin nerves. In conclusion, VR1 is widely distributed in the skin, suggesting a major role for this receptor, e.g. in nociception and neurogenic inflammation.