Induction and localization of cutaneous interleukin-1 beta mRNA during contact sensitization

Immune-Regulatory and Molecular Effects of Antidepressants on the Inflamed Human Keratinocyte HaCaT Cell Line

Allergic contact dermatitis (ACD) is a T cell-mediated type of skin inflammation resulting from contact hypersensitivity (CHS) to antigens. There is strong comorbidity between ACD and major depression. Keratinocytes release immunomodulatory mediators including pro-inflammatory cytokines and chemokines, which modulate skin inflammation and are crucial cell type for the development of CHS. Our previous studies showed that fluoxetine and desipramine were effective in suppressing CHS in different mouse strains. However, the immune and molecular mechanisms underlying this effect remain to be explored. The aim of the current study was to determine the immune and molecular mechanisms of action of antidepressant drugs engaged in the inhibition of CHS response in the stimulated keratinocyte HaCaT cell line. The results show that LPS, TNF-α/IFN-γ, and DNFB stimulate HaCaT cells to produce large amounts of pro-inflammatory factors including IL-1β, IL-6, CCL2, and CXCL8. HaCaT stimulation was associated with increased expression of ICAM-1, a cell adhesion molecule, and decreased expression of E-cadherin. Imipramine, desipramine, and fluoxetine suppress the production of IL-1β, CCL2, as well as the expression of ICAM-1. LPS and TNF-α/IFN-γ activate p-38 kinase, but antidepressants do not regulate this pathway. LPS decreases E-cadherin protein expression and fluoxetine normalizes these effects. In summary, the antidepressant drugs examined in this study attenuate the stimulated secretion of pro-inflammatory cytokines, chemokines, and modulate adhesion molecule expression by the HaCaT cell line. Therefore, antidepressants may have some clinical efficacy in patients with ACD and patients with comorbid depression and contact allergy.

Induction of IL-1β and antimicrobial peptides as a potential mechanism for topical dithranol

Topical dithranol is effective in autoimmune conditions like alopecia areata, inducing hair regrowth in a high percentage of cases. Exact mechanisms of dithranol in alopecia areata, with seemingly healthy epidermis besides altered hair follicles, are not well understood. To better understand dithranol's mechanisms on healthy skin, we analysed its effect on normal murine as well as xenografted human skin. We found a strong increase in mRNA expression of anti-microbial peptides (AMPs) (eg Lcn2, Defb1, Defb3, S100a8, S100a9), keratinocyte differentiation markers (eg Serpinb3a, Flg, Krt16, Lce3e) and inflammatory cytokines (eg Il1b and Il17) in healthy murine skin. This effect was paralleled by inflammation and disturbed skin barrier, as well as an injury response resulting in epidermal hyperproliferation, as observed in murine and xenografted adult human skin. This contact response and disturbed barrier induced by dithranol might lead via a vicious loop between AMPs such as S100a8/a9 (that led to skin swelling itself after topical application) and cytokines such as IL-1β to an immune suppressive environment in the skin. A better understanding of the skin's physiologic response to dithranol may open up new avenues for the establishment of novel therapeutics (including AMP-related/interfering molecules) for certain skin conditions, such as alopecia areata.

NLRP3 Inflammasome and Allergic Contact Dermatitis: A Connection to Demystify

Allergic contact dermatitis is a common occupational disease that manifests as a cell-mediated hypersensitivity reaction following skin exposure to small reactive chemicals termed haptens. Haptens penetrate the stratum corneum and covalently modify proteins in the epidermis, inducing intracellular stress, which further leads to the release of damage-associated molecular patterns (DAMPs), such as uric acid, reactive oxygen species, hyaluronic acid fragments and extracellular adenosine triphosphate (ATP). These DAMPs are recognized by pattern recognition receptors (PRRs) in innate immune cells, namely dendritic cells (DCs), leading to their maturation and migration to the draining lymph nodes where they activate naïve T lymphocytes. Among all PRRs, several studies emphasize the role of NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome on the allergic contact dermatitis (ACD) sensitization phase. However, skin allergens-danger signals-NLRP3 inflammasome axis is yet to be completely elucidated. Therefore, in this review, we sought to discuss the molecular mechanisms underlying DAMPs release and NLRP3 inflammasome activation triggered by skin allergens. The elucidation of these key events might help to identify novel therapeutic strategies for ACD, as well as the development of nonanimal alternative methods for the identification and potency categorization of skin sensitizers.

The balance between pro- and anti-inflammatory cytokines is crucial in human allergic contact dermatitis pathogenesis: the role of IL-1 family members

The interleukin (IL)-1 family includes 11 members that are important in inflammatory processes. It includes various agonists and two antagonists, IL-1Ra and IL-36Ra. Our aim was to investigate whether the IL-1 family is involved in allergic contact dermatitis (ACD). The expression of IL-1 family members was evaluated by PCR and immunohistochemistry in the positive patch test reaction site (involved skin) and in the uninvolved skin of ACD patients. We also examined these cytokines in an ex vivo model of ACD. The antagonistic activity of IL-36Ra was evaluated by injecting recombinant IL-36Ra in uninvolved skin biopsies of ACD patients. IL-1Ra and IL-36Ra expression was quantified in mononuclear cells of nickel-sensitized patients challenged in vitro with nickel. IL-33 involvement in ACD was investigated by intra-dermal injection of anti-IL-33 in the uninvolved skin of patients ex vivo. Results showed that IL-1β, IL-1Ra, IL-36α, IL-36β, IL-36γ and IL-33 expression, but not IL-36Ra expression, was enhanced in ACD-involved skin. Immunohistochemical analysis and ex vivo skin cultures confirmed these results. Injection of anti-IL-33 in ACD-uninvolved skin inhibited IL-8 expression, whereas IL-36Ra inhibited IL-36α, IL-36β, IL-36γ and IL-8 expression. Nickel induced IL-1Ra expression in lymphocytes of nickel-sensitized patients. Hence, various IL-1 agonists and antagonists may be involved in ACD pathogenesis.

IL-1 receptor signaling is required at multiple stages of sensitization and elicitation of the contact hypersensitivity response

Contact hypersensitivity (CHS) is a CD8 T cell-mediated response to hapten skin sensitization and challenge. The points at which IL-1R signaling is required during this complex, multistep immune response have not been clearly delineated. The role of IL-1R signaling during 2, 4 dinitro-1-fluorobenezene (DNFB) sensitization to induce hapten-specific CD8 effector T cells and in the trafficking of the effector T cells to the DNFB challenge site to elicit the response were investigated using IL-1R deficient mice. DNFB-sensitized IL-1R(-/-) mice had low CHS responses to hapten challenge that were caused in part by marked decreases in hapten-specific CD8 T cell development to IL-17- and IFN-γ-producing cells during sensitization. Hapten-primed wild type CD8 T cell transfer to naive IL-1R(-/-) mice did not result in T cell activation in response to hapten challenge, indicating a need for IL-1R signaling for the localization or activation, or both, of the CD8 T cells at the challenge site. Decreased CD8 T cell priming in sensitized IL-1R(-/-) mice was associated with marked decreases in hapten-presenting dendritic cell migration from the sensitized skin to draining lymph nodes. Transfer of hapten-presenting dendritic cells from wild type donors to naive IL-1R(-/-) mice resulted in decreased numbers of the dendritic cells in the draining lymph nodes and decreased priming of hapten-specific CD8 T cells compared with dendritic cell transfer to naive wild type recipients. These results indicate that IL-1R signaling is required at multiple steps during the course of sensitization and challenge to elicit CHS.

In vitro and in vivo analysis of pro- and anti-inflammatory effects of weak and strong contact allergens

Inflammation is a crucial step in the development of allergic contact dermatitis. The primary contact with chemical allergens, called sensitization, and the secondary contact, called elicitation, result in an inflammatory response in the skin. The ability of contact allergens to induce allergic contact dermatitis correlates to a great extent with their inflammatory potential. Therefore, the analysis of the sensitizing potential of a putative contact allergen should include the examination of its ability and potency to cause an inflammation. In this study, we examined the inflammatory potential of different weak contact allergens and of the strong sensitizer 2,4,6-trinitrochlorobenzene (TNCB) in vitro and in vivo using the contact hypersensitivity model, the mouse model for allergic contact dermatitis. Cytokine induction was analysed by PCR and ELISA to determine mRNA and protein levels, respectively. Inflammation-dependent recruitment of skin-homing effector T cells was measured in correlation with the other methods. We show that the sensitizing potential of a contact allergen correlates with the strength of the inflammatory response. The different methods used gave similar results. Quantitative cytokine profiling may be used to determine the sensitizing potential of chemicals for hazard identification and risk assessment.

IL-1 and Allergy

IL-1 is a well-characterized proinflammatory cytokine that is involved in host defense and autoimmune diseases. IL-1 can promote activation of T cells, including Th1 cells, Th2 cells and Th17 cells, and B cells, suggesting that IL-1 may contribute to the development of various types of T-cell-mediated diseases. This report reviews and discusses the role of IL-1 in the pathogenesis of allergic diseases based on studies using IL-1-related gene-deficient mice.

Topical p38MAPK inhibition reduces dermal inflammation and epithelial apoptosis in burn wounds

Thermal injury induces dermal inflammatory and proapoptotic signaling. These phenomena extend burn wound size and trigger a systemic inflammatory response, factors known to adversely affect outcomes. p38MAPK is known to trigger inflammatory responses and induce epithelial proapoptotic genes. We hypothesize that topical p38MAPK inhibition will attenuate excessive inflammatory and apoptotic signaling and reduce dermal tissue loss. Rats were given a 30% total body surface area partial thickness burn or sham injury. Some of the animals were treated with a p38MAPK inhibitor or vehicle, which was applied directly to the wound. Dermal inflammation was investigated with enzyme-linked immunosorbent assay, reverse transcriptase polymerase chain reaction, myeloperoxidase assay, and Evans blue extravasation. Apoptotic changes were detected using terminal deoxynucleotidyl transferase dUTP nick-end labeling assay and Caspase-3 in situ staining. Burn injury activated dermal p38MAPK and induced a significant rise in dermal IL-6, TNF-alpha, and IL-1beta expression. Neutrophil sequestration, microvascular damage, and hair follicle apoptosis were significantly elevated after injury. Topical p38MAPK inhibition significantly attenuated downstream dermal p38MAPK targets, proinflammatory cytokine expression, neutrophil sequestration, and microvascular injury. A significant reduction in hair follicle apoptosis was seen. This study demonstrates the attenuation of burn-induced cellular stress by topical application of p38MAPK inhibitors. Blunting early excessive inflammatory signaling may be an efficient strategy to improve patient outcomes after burn injury.

Effects of indomethacin and dexamethasone on mechanical scratching-induced cutaneous barrier disruption in mice

Effects of indomethacin and dexamethasone on recovery of cutaneous barrier disruption induced by mechanical scratching were examined. Cutaneous barrier was disrupted by scratching using a stainless-steel wire brush (mechanical scratching) and compared to cutaneous application of acetone/ether (1:1) mixture (AE) and tape-stripping. Increase of transepidermal water loss (TEWL), as an indicator of a broken skin barrier, and recovery period for mechanical scratching were higher and longer than those for AE treatment and tape-stripping and we also confirmed the severity of skin damage in a histological study. Topical application of moisturizers showed a temporal effect, rapidly decreased TEWL on mechanical scratching- or AE treatment-induced cutaneous barrier disruption, and gradually increased base levels from 4 to 12 h after treatment. Topical application of indomethacin or dexamethasone prolonged the recovery period for the cutaneous barrier, and concomitant use further worsened the status of the barrier. Additionally, we examined the effects of prostaglandins (PGs) and inflammatory cytokine on mechanical scratching-induced cutaneous barrier disruption pretreated with indomethacin and dexamethasone. As a results, PGD2 and interleukin (IL)-1beta significantly accelerated the recovery of cutaneous barrier disruption by mechanical scratching but such was not the case with PGE2, IL-1alpha, and tumor necrosis factor-alpha treatment. These results suggest that indomethacin and dexamethasone prolonged the recovery period caused by inhibition of PGD2 and IL-1beta. Mechanical scratching-induced cutaneous barrier disruption may be a useful method for evaluating means of recovery from skin damage.

Aqueous extract from aerial parts of Artemisia vestita, a traditional Tibetan medicine, reduces contact sensitivity in mice by down-regulating the activation, adhesion and metalloproteinase production of T lymphocytes

In the present paper, the effect of the aqueous extract from aerial parts of Artemisia vestita (AV-ext), a traditional Tibetan medicine, on ear contact sensitivity was examined. AV-ext significantly reduced the ear swelling when administered during the induction phase of picryl-chloride (PCl)-induced ear contact sensitivity in mice. The extract also showed a dose-dependent inhibition on lymphocyte proliferation and IL-2 production in Con A-activated spleen cells. The proliferation inhibition was confirmed in the mixed lymphocytes reaction. Furthermore, the adhesion of the isolated spleen cells from PCl-sensitized mice to type IV collagen was significantly decreased in a dose-dependent manner by AV-ext. Such decrease was also seen in AV-ext-treated Jurkat T cells and the T cells purified from above spleen cells. The purified spleen T cells from PCl-sensitized mice produced more matrix metalloproteinase-9 (MMP-9) than naive T cells, and AV-ext remarkably reduced MMP-9 production both in vivo and in vitro. These results suggest that AV-ext may alleviate contact sensitivity through blocking the activation of T lymphocytes and decreasing their localization to the inflammatory sites via down-regulating the potential of cell adhesion and metalloproteinase production.

Anti-vascular endothelial growth factor receptor-2 (Flk-1/KDR) antibody suppresses contact hypersensitivity

The angiogenic mediator vascular endothelial growth factor (VEGF) and its receptors (VEGFRs) have been studied extensively in neoplastic disease and some inflammatory conditions. Contact hypersensitivity (CHS) is a prototypic Langerhans' cell-dependent, T-helper (Th) 1 cell-mediated inflammatory skin disease that is now also thought to involve angiogenic mediators. The purpose of our study was to examine the role of angiogenesis and VEGF in CHS. We demonstrated that VEGF production is up-regulated in murine skin after challenge with dinitrofluorobenzene. Administration of a monoclonal antibody directed against the VEGFR-2 (DC101) resulted in a 28.8% decrease in CHS response (P < 0.001). Examination of the DC101-treated mouse skin 24 h after challenge revealed decreases in dermal inflammatory cellular infiltrates and total vessel area. Furthermore, mRNA and protein of the Th1-type cytokine interferon (IFN)-gamma was significantly down-regulated in skin of DC101-treated animals 24 h after challenge. The results of the study demonstrate that VEGFR-2 blockade significantly reduces vascular enlargement and edema formation and effects IFN-gamma expression in the skin during challenge in CHS. Our findings suggest that DC101 could function by reducing inflammatory cell migration and hence IFN-gamma expression during the CHS response.

Epistatic effect of IL1A and IL4RA genes on the risk of atopy

BACKGROUND

Several studies have demonstrated a linkage or association of the atopic phenotype with T-cell cytokine genes involved in the regulation of the TH1/TH2 balance (eg, IL4, IL13, and their common receptor, IL4RA). We have recently shown that polymorphism of the pro-inflammatory cytokine IL1A gene is strongly associated with atopy.

OBJECTIVE

We now examined whether the polymorphisms of IL1A (G/T at +4845) and IL4RA (T/C at +22446) would show an epistatic effect on the risk of atopy.

METHODS

Skin prick tests and gene polymorphism analyses were performed in a population-based sample of asthmatic and nonasthmatic subjects.

RESULTS

Our results showed that in the nonasthmatic group the previously described elevated risk of atopy in noncarriers of allele T of IL1A (ie, having the genotype GG) was restricted to individuals who were also noncarriers of allele C of IL4RA (genotype TT). This finding applies to the general population of Finland, where 3.3% of adults are asthmatic.

CONCLUSION

These data suggest that the IL1A and IL4RA genes show an epistatic effect on the risk of atopy.

Characterization of the Sensitizing Potential of Chemicals by In Vitro Analysis of Dendritic Cell Activation and Skin Penetration

Development of in vitro models to identify sensitizing chemicals receives public interest since animal testing should be avoided whenever possible. In this article we analyze two essential properties of sensitizing chemicals: skin penetration and dendritic cell (DC) activation. Activation of immature DC derived from peripheral blood monocytes was evaluated by flow cytometric analysis of CD86 positive cells and quantitative measurement of interleukin-1beta and aquaporin P3 gene expression. The sensitizer 2,4,6-trinitrobenzenesulfonic acid induced a concentration-dependent response for all parameters, whereas the irritant sodium lauryl sulfate did not. When two related aromatic amines, p-toluylenediamine (PTD) and hydroxyethyl-p-phenylenediamine (HE-PPD) were tested, both induced substantial DC activation indicating their potential sensitizing properties. These findings contrasted with in vivo results: in murine local lymph node assays (LLNA) PTD, but not HE-PPD, was sensitizing using acetone/aqua/olive oil as vehicle. Skin penetration measurement revealed that this was due to bioavailability differences. On retesting HE-PPD in the LLNA using the penetration enhancer dimethylsulfoxide as vehicle, it induced a specific response. We conclude that in vitro analysis of DC activation capability of the two selected chemicals demonstrates that prediction of skin sensitization potential is possible provided that skin penetration data indicate sufficient bioavailability of the test compound.

The IL1A genotype associates with atopy in nonasthmatic adults

BACKGROUND

The skin prick test is used to examine specific IgE-mediated allergic responses. Generally, results accord well with anamnestic information on atopy. Several genetic factors probably affect the strength of allergen-mediated skin test reactions.

OBJECTIVE

We sought to investigate skin test findings in a population-based sample of adult asthmatic patients and control subjects and to establish whether the IL1A genotype affects allergy testing.

METHODS

We analyzed the single G-to-T base exchange polymorphism in exon 5 at +4845 of the gene encoding IL-1alpha (IL1A) in adult asthmatic patients (n = 245) and nonasthmatic control subjects (n = 405). The data were assessed for correlation with data on the skin test responses of these subjects to 22 common allergens.

RESULTS

The IL1A genotype distribution and allele frequencies proved similar in patients and control subjects. Surprisingly, the IL1A genotype distribution was markedly different in control subjects with positive (ie, >/=1 positive reaction) and negative skin test responses (P =.006). This difference was caused by an increase in the frequency of the rarer allele 2 in control subjects with negative skin test responses (P =.004).

CONCLUSION

Our study demonstrates that the IL1 gene complex is involved in the regulation of IgE-mediated atopic reactions. The results suggest that skin test responses to specific allergens are differently regulated in nonasthmatic and asthmatic subjects. Because of the potential role of the IL1A genotype as a confounding factor in skin prick testing, these results require special attention and should be further evaluated in other clinical settings.