Tachykinin upregulation in atopic dermatitis.

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

Serotonergic Markers in Atopic Dermatitis.

Stress and anxiety may worsen atopic dermatitis (AD) through the serotonin system. Serotonergic expression was measured in 28 patients with AD in relation to extent of the disease (SCORing of Atopic Dermatitis; SCORAD), pruritus intensity (visual analogue scale; VAS), anxiety traits (Swedish Universities Scales of Personality; SSP) and depression (Montgomery-Åsberg Depression Rating Scale-Self assessment; MADRS-S). Biopsies were taken from lesional and non-lesional AD skin, and investigated for expression of serotonin, its receptors 5-HT1A and 5-HT2, and serotonin transporter protein (SERT), using immunohistochemistry. 5-HT1AR-immunoreactivity (ir) was higher in lesional skin in apical epidermis and in mast cell-like cells in dermis, and 5-HT2AR-ir in apical epidermis and on blood vessels. In contrast, a basement membrane 5-HT2AR-ir signal was higher in non-lesional skin. The distribution of SERT-ir in the basal epidermal layer was higher in lesional skin. Positive and negative correlations were found between serotonergic markers and SCORAD, inflammation, pruritus intensity, anxiety traits, and depression score, indicating that serotonergic mechanisms are involved in AD.

Serotonin and its 5-HT1 receptor in human mastocytosis.

CONTEXT: Human mastocytosis is a rare disease, in which the serotonergic system may be involved. OBJECTIVE: The objective of the present study was to examine the possible presence of serotonin (5-HT) and its 5-HT1A receptor (R) in the skin of patients with mastocytosis. In addition, the effect of the 5-HT1AR was tested on human mastocytosis cells, cultured in vitro. MATERIALS AND METHODS: The expression of 5-HT and 5-HT1AR in patients with urticaria pigmentosa and mastocytoma was studied using immunohistochemistry. The effects of 8-OH-DPAT, an agonist of 5-HT1AR, on the proliferation (cell number), viability, apoptosis, spontaneous release of histamine, as well as a possible 5-HT metabolism, in the human HMC-1 mast cell line, were investigated. RESULTS: Both 5-HT and 5-HT1AR were expressed in the mast cells in biopsies of mastocytoma and urticaria pigmentosa, as well as in HMC-1 cells. However, no metabolism of 5-HT by the cell line could be detected by the methodology used. The 5-HT1AR agonist had no significant effect on the viability and number of HMC-1 cells, and was without effect on the apoptosis. At concentrations of 10⁻6 mol/L and 10⁻8-10⁻¹° mol/L (i.e. also at physiological concentrations), the agonist inhibited histamine release by these cells by as much as 30%. CONCLUSION: These findings indicate that 5-HT and its 5-HT1AR are expressed in human mastocytosis and that an agonist of the 5-HT1AR might be of value in the treatment of these patients.

Decreased innervation of eczematous skin in NC/Nga atopic mice during chronic mild stress.

BACKGROUND AND AIM: A connection between chronic mild stress and altered innervation in the skin of an atopic mouse strain, NC/Nga, was studied. MATERIAL AND METHODS: We used three groups of mice, stressed control (SC, stressed but not immunized with a mite antigen), non-stressed eczematous (NSE, not stressed but immunized) and stressed eczematous (SE, stressed and immunized). RESULTS: There was a decrease of protein gene product (PGP) 9.5 positive nerve fibers in SE compared to SC mice, in both epidermis and dermis, also in SE compared to NSE mice. Also a decrease in growth associated protein (GAP)-43 positive nerve fibers was seen in SE compared to SC, in both epidermis and dermis. CONCLUSION: Chronic mild stress in atopic mice leads to decreased innervation in eczematous lesions.

Expression of serotonin receptors in allergic contact eczematous human skin.

The expression of the serotonin (5-HT) receptors 5-HT1AR, 5-HT2AR and 5-HT3R was investigated in allergic contact eczematous human skin by an indirect fluorescence method. 5-HT1AR expression was found in basal epidermal NK1-beteb-positive cells, which were more elongated and showed longer dendritic processes in contact eczematous skin than in control skin. Immunoreactivity for 5-HT1AR was also found in the upper part of the epidermis, with no difference between eczematous and control skin. 5-HT1AR expression was also found in 33.3+/-6.5% and 63.7+/-11.3% of papillary dermal mononuclear cells in inflamed skin and control skin, respectively ( P<0.001), as well as in vessel walls. Some of these mononuclear cells were tryptase-positive, and found in both eczematous and control skin. 5-HT2AR-positive cells were found in the upper part of the epidermis in eczematous skin, but were more evenly distributed in the epidermis of control skin. In addition, inflammatory dermal mononuclear cells and vessel walls showed immunoreactivity for this receptor. 5-HT3R expression was found in the basal epidermal layer of eczematous and control skin. These findings indicate a plasticity in the effects of serotonin, especially regarding 5-HT1AR, in allergic contact eczematous skin.

Chronic mild stress modulates 5-HT1A and 5-HT2A receptor expression in the cerebellar cortex of NC/Nga atopic-like mice.

Atopic eczema symptoms may worsen due to stress. In the present study, the cerebellar cortex of the atopic-like mouse NC/Nga was studied regarding the effect of chronic mild stress on expression of two well-characterized serotonergic receptors (R), 5-HT1A and 5-HT2A. In total 24 mice were used. Sixteen of these mice were subjected to unpredictable stressors for 12 weeks, and 8 mice were used as controls. In order to evoke an eczema, a mite antigen was applied to 16 mice from week 9 of the experiment. Thus, three groups of mice, stressed eczematous (SE), non-stressed eczematous (NSE) and stressed control (SC), respectively, were obtained. The expression of the 5-HT1AR was analyzed using quantitative immunohistochemistry. For evaluation of 5-HT2AR a semi-quantitative technique was used, the cell density and signal intensity being measured. The highest average value for 5-HT1AR expression, in the Purkinje cells, was recorded in the NSE group, while the lowest average was in the SC group. 5-HT1AR expression differed significantly between the groups. The highest average value for density of 5-HT2AR positive Purkinje cells was evident in the SE group, while the lowest was in the SC group, this difference between groups also being statistically significant. In addition, the signal intensity was highest in the SE group, with a difference compared to the other groups. In conclusion, chronic mild stress modulates serotonergic receptor expressions in the cerebellar cortex of atopic-like mice.

Kinetics of neuronal contribution during the development of a contact allergic reaction.

The nervous system contributes to allergic contact dermatitis (ACD). Elucidation of the implication of the nervous system during different stages of ACD could be of therapeutic value. Our aim was to study the kinetics and contribution of the nervous system to ACD by investigating innervation and expression of neuropeptides in skin biopsies obtained at 0, 6, 24, 48 and 72 h post-challenge. Biopsies were stained using antisera against protein gene product (PGP) 9.5, growth associated protein (GAP)-43, substance P and its receptor (R) neurokinin (NK)-1, NKA and NK-2R, and calcitonin gene-related peptide (CGRP). GAP-43-immunoreactive (ir) nerves revealed a time-dependent increase that was more pronounced at 48 and 72 h, while PGP 9.5-ir nerves remained unaltered. Substance P-, NKA- and CGRP-ir nerves at 0 and 6 h were significantly higher compared to later time points, whereas NKA-, NK-1R- and NK-2R-ir cells were lower. A dramatic rise in cell numbers was noted at 24 h. Our findings demonstrate the implication of nerves and sensory neuropeptides during the kinetics of ACD and suggest a possibility to target this system at an early time point for therapy.

Effect of chronic mild stress on serotonergic markers in the skin and brain of the NC/Nga atopic-like mouse strain.

Atopic eczema is often worsened by stress. While acute stress is associated with increased turnover of serotonin (5-hydroxytryptamine; 5-HT), chronic stress causes a decrease. In chronic stress, there is a decrease of the 5-HT1A receptor (R)- and an increase in the 5-HT2AR-responsiveness to 5-HT. In the present study, the impact of chronic mild stress on the expression of 5-HT1A and 5-HT2A receptors and serotonin transporter protein (SERT) was investigated in eczematous skin and brain of atopic-like NC/Nga mice. Twenty-four NC/Nga mice were subjected to chronic mild stress for 12 weeks, and eczema was induced by applying a mite antigen (Dermatophagoides pteronyssinus) on the ears for the last 4 weeks. The mice were divided into three groups, eight per group, stressed eczematous (SE), non-stressed eczematous (NSE) and stressed control (SC). The biopsies were analysed by immunohistochemistry, using a streptavidin-biotin technique. There was an increased number of 5-HT containing dermal mast cell-like mononuclear cells in the skin of mice with eczema (SE and NSE, respectively) compared with the SC, and a tendency to more 5-HT-positive cells in the SE compared with the NSE group. Increased 5-HT1AR immunoreactivity (IR) in the skin and hippocampus of the eczematous groups compared to the control group was seen, but no difference between the SE and NSE groups. The epidermal immunoreactivity for 5-HT2AR was highest in the SE and NSE compared to the SC group, and was also higher in the SE compared to NSE. 5-HT2AR expression was also seen on nerve bundles, the number and intensity of such bundles being decreased in the SE compared to the NSE group. In the CA1 area of the hippocampus, there was an increase in the quantity of cells immunoreactive for 5-HT2AR in the SE versus the NSE group and also in the SE versus the SC group. SERT-IR was found also on nerve bundles with a decreased number in the SE compared to the NSE and SC group. There is a modulation of the expression of serotonergic markers in the eczematous skin and brain of the atopic-like mouse during chronic mild stress.

GABA and GABA(A) receptor expression on immune cells in psoriasis: a pathophysiological role.

Psoriasis is a chronic inflammatory disease in which pruritus is a common symptom. Pruritus may be associated with the gamma-aminobutyric acid (GABA) system. The distribution of GABA and its GABA(A) receptor (R) was studied in involved and non-involved psoriatic skin, as well as normal healthy control skin, using an immunohistochemistry technique. Pruritus was determined using a visual analog scale. Inflammatory cells immunoreactive for the GABA ligand and the GABA(A) R were increased (P < 0.01, respectively) in the involved skin. Cells stained for GABA ligand were mostly macrophages with some lymphocytes, while cells stained for GABA(A) R were macrophages, neutrophils or lymphocytes. There was a positive correlation when comparing GABA ligand (P = 0.05) and GABA(A) R (P < 0.05) expressing inflammatory cells, with pruritus. The GABA ligand and its GABA(A) R may play a role for the pathogenesis of psoriasis as well as for pruritus in this disease.

Different serotonergic expression in nevomelanocytic tumors.

The neuromediator serotonin (5-hydroxytryptamine; 5-HT) has been proposed to play a role in tumor progression. Thus, the aim of the present investigation was to determine whether alterations in the serotonergic system occur in nevomelanocytic tumors. For this purpose, paraffin-embedded biopsies of superficial spreading malignant melanoma (SSM), dysplastic compound nevi (DN) and benign compound nevi (BCN) were characterized with regard to their expression of 5-HT, the 5-HT1A and 5-HT2A receptors, and the serotonin transporter protein (SERT), by immunohistochemical analysis. Melanocytes in the region surrounding the tumor were found to express both the 5-HT1A and 5-HT2A receptors. Tumor cells that immunostained positively for the different serotonergic markers were observed in the suprabasal epidermis of DN tissue and, to an even greater extent, in the case of SSM. Furthermore, some of these latter cells expressed both 5-HT1AR and 5-HT2AR. The level of expression of 5-HT1AR at the junctional area was lower for SSM than for DN or BCN. As the degree of atypia increased, the intensity of tumor cell staining in the dermis for 5-HT1AR and SERT declined. Vessel immunoreactivity for 5-HT2A was more intense in SSM than in BCN tissue. Round-to-dendritic cells that expressed both SERT and 5-HT1AR were seen to infiltrate into the dermal region of the tumor, this infiltration being more evident in the case of DN and SSM. These latter cells were also tryptase-positive, indicating that they are mast cells. Thus, alterations in serotonergic system may be involved in nevomelanocytic tumors and mast cells may play an important role in this connection.

The serotonin transporter protein is expressed in psoriasis, where it may play a role in regulating apoptosis.

Since the symptoms of psoriasis may be changed by treatment with selective serotonin reuptake inhibitors (SSRIs), the expression of serotonin (5-HT) and its transporter protein (SERT) in the skin of patients with psoriasis were examined employing a biotinylated-streptavidine procedure. In biopsies of such skin staining for 5-HT was limited to platelets; the expression of SERT in the keratinocytes of involved regions was redistributed; the numbers of SERT-positive dendritic or round mononuclear cells in the epidermis of involved psoriatic skin were higher than in normal healthy control skin; and the dermis of the involved skin contained higher numbers of round inflammatory cells immunostained for SERT than either non-involved psoriatic skin or normal skin. Double-immunostaining indicated that the skin cells expressing SERT also expressed CD1a, CD3 or tryptase. In addition, SERT immunostaining was co localized with caspase-3, a key regulator of apoptosis, but not with TUNEL staining. The present findings indicate that SERT might play a role in regulating apoptosis in inflammatory cells associated with psoriasis, in which case this protein might constitute a valuable therapeutic target.

The expression and functional significance of the serotonin(2C) receptor in murine contact allergy.

Serotonin (5-hydroxytryptamine, 5-HT) was proposed to modulate murine contact allergy by binding to 5-HT(1A/2A) receptors (R). We examined the expression of 5-HT(2C)R in the skin of mice with contact allergy, as well as the effects of an agonist and antagonist of this receptor on the elicitation phase of this type of allergy. Immunohistochemistry revealed the presence of 5-HT(2C)R on epidermal dendritic cells, and in the inflamed skin the cells expressing this antigen were increased in number (P < 0.01) and exhibited longer dendrites than in the control tissue. Furthermore, the majority of these cells also stained positively for I-A, a specific marker for Langerhans cells (LCs). Treatment of the skin of sensitized mice in vivo with RO60-0175 (0.5 and 1.0 mg/kg, once daily for 3 days prior to the challenge with antigen), an agonist for 5-HT(2C)R, enhanced the degree of contact eczema (P < 0.05 and P < 0.01 for the two doses respectively), as indicated by ear thickness. This enhancement could be prevented (P < 0.001) by the 5-HT(2C)R antagonist SB 242084 at 3 mg/kg. Addition of 5 x 10(-5) mol/l RO60-0175 to murine XS52 cells, which resembles LCs, potentiated their secretion of interleukin (IL)-1beta (P < 0.05); whereas 10(-10) mol/l attenuated this secretion (P < 0.05). Under the same conditions, the level of IL-1beta mRNA in these cells (as assessed by RT-PCR) was unaltered suggesting that this agonist may exert its effect on IL-1beta secretion at the post-transcriptional or even at the secretory level. In conclusion, our findings indicate that the 5-HT(2C)R is involved in modulating contact allergy in mice.

Serotonergic mechanisms in human allergic contact dermatitis.

Expression of serotonin (5-hydroxytryptamine; 5-HT), 5-HT receptors 1A (5-HT1AR) and 2A, and serotonin transporter protein (SERT) was studied in positive epicutaneous reactions to nickel sulphate in nickel-allergic patients, at 72 h post-challenge with the antigen. In addition, the effects of 5-HT2AR agonist 2,5-dimethoxy-4-iodoamphetamine (DOI), and the selective serotonin reuptake inhibitors (SSRIs) citalopram and fluoxetine, were tested on nickel-stimulated peripheral blood mononuclear cells from nickel-allergic patients, regarding their proliferation and interleukin (IL)-2 production, as well as the effect of these SSRIs on a murine Langerhans' cell-like line (XS52), regarding its IL-1beta production. Serotonin-positive platelets were increased in the inflamed skin compared with control skin. A decrease (p <0.01) in 5-HT1AR-positive mononuclear cells was evident in the eczematous skin compared with control skin, whereas 5-HT2AR- and SERT-positive cells were increased (p <0.001 for both) in the eczematous skin. Treatment of nickel-stimulated peripheral blood mononuclear cells with 5x10(-5) mol/l of DOI inhibited (p <0.01) the proliferation of nickel-stimulated peripheral blood mononuclear cells, while no effect was found regarding IL-2 production. Citalopram at 10(-6) mol/l tended to inhibit the production of IL-1beta by the XS52 cell line. These results indicate the implication of the serotonergic system in the contact allergic reaction.

Galanin expression in a murine model of allergic contact dermatitis.

Galanin is a neuropeptide widely distributed in the nervous system. The expression of galanin was investigated in murine contact allergy using immunohistochemistry, radioimmunoassay and in situ hybridization. Female BALB/c mice were sensitized with oxazolone and 6 days later challenged on the dorsal surface of ears, while control mice received vehicle. After 24 h, one ear was processed for immunostaining using a biotinylated fluorescence technique, while the other ear was frozen and processed for radioimmunoassay or in situ hybridization. Galanin immunoreactive nerve fibres were more numerous (p < 0.01) in the eczematous compared with control ears. Double-staining with antibody to the nerve fibre marker PGP (protein gene product) 9.5 revealed colocalization of PGP 9.5 and galanin in nerve fibres. Radioimmunoassay demonstrated a decrease (p < 0.04) in galanin concentration in eczematous compared with control ears. Our results suggest a role for galanin in murine contact allergy.