Horizons in pharmacologic intervention in allergic contact dermatitis

CXCR3 chemokine receptor signaling mediates itch in experimental allergic contact dermatitis

Persistent itch is a common symptom of allergic contact dermatitis (ACD) and represents a significant health burden. The chemokine CXCL10 is predominantly produced by epithelial cells during ACD. Although the chemokine CXCL10 and its receptor CXCR3 are implicated in the pathophysiology of ACD, it is largely unexplored for itch and pain accompanying this disorder. Here, we showed that CXCL10 and CXCR3 mRNA, protein, and signaling activity were upregulated in the dorsal root ganglion after contact hypersensitivity (CHS), a murine model of ACD, induced by squaric acid dibutylester. CXCL10 directly activated a subset of cutaneous dorsal root ganglion neurons innervating the area of CHS through neuronal CXCR3. In behavioral tests, a CXCR3 antagonist attenuated spontaneous itch- but not pain-like behaviors directed to the site of CHS. Injection of CXCL10 into the site of CHS elicited site-directed itch- but not pain-like behaviors, but neither type of CXCL10-evoked behaviors was observed in control mice. These results suggest that CXCL10/CXCR3 signaling mediates allergic itch but not inflammatory pain in the context of skin inflammation. Thus, upregulation of CXCL10/CXCR3 signaling in sensory neurons may contribute to itch associated with ACD. Targeting the CXCL10/CXCR3 signaling might be beneficial for the treatment of allergic itch.

Enhanced scratching elicited by a pruritogen and an algogen in a mouse model of contact hypersensitivity

Chemical pruritogens and algogens evoke primarily itch and pain, respectively, when administered to the skin of healthy human subjects. However, the dominant sensory quality elicited by an algesic chemical stimulus may change in patients with chronic itch where bradykinin, elicits itch in addition to pain. Here we tested whether normally pruritic and algesic chemicals evoked abnormal itch- or pain-like behaviors in the mouse after the development of contact hypersensitivity (CHS), an animal model of allergic contact dermatitis. Mice previously sensitized to a hapten (squaric acid dibutylester) applied to the abdomen, exhibited spontaneous itch-like scratching and pain-like wiping directed to the site on the cheek of the CHS elicited by a subsequent challenge with the same hapten. In comparison with responses of control mice, CHS mice exhibited a significant increase in the scratching evoked by bovine adrenal medulla 8-22, a peptide that elicits a histamine-independent itch, but did not alter the scratching to histamine. Bradykinin, an algogen that elicited only wiping in control mice, additionally evoked significant scratching in CHS mice. Thus, within an area of CHS, histamine-independent itch is enhanced and chemically evoked pain is accompanied by itch.

Tacrolimus: 10 years of successful clinical application

Tacrolimus (FK506) is the first drug from the new class of drugs - calcineurin inhibitors. It has a great potential and can change the current approaches to treatment of different dermatoses. Topical forms of Tacrolimus are activated due to the effect on T-lymphocyte signal transduction, and they also inhibit gene transcription. As a result, the T-cell response to antigens is alleviated. Percutaneous absorption of Tacrolimus in affection foci is higher than in healthy skin. Due to this a smaller amount of the drug is absorbed by the skin as long as the skin is healed. Systemic absorption of Tacrolimus is low in the course of treatment. The maximum clinical experience has been gained in the field of applying Tacrolimus for treatment of atopic dermatitis. In a number of clinical studies, 0.03-0.3% Tacrolimus ointment efficiently reduced the severity of symptoms and course of atopic dermatitis in adults and children. Moreover, topical treatment with Tacrolimus did not involve any substantial toxic effects. The patients most often complained of local irritations in the area where the ointment was applied, which were transient by nature and did not demand the drug withdrawal. Today Tacrolimus is a valuable and safer alternative to glucocorticosteroids for treatment of atopic dermatitis. It can also be used for treating other dermatoses, which demands additional all-round examination.

A randomized controlled trial: is water better than a standard lubricant in nasendoscopy?

OBJECTIVES

Previous studies have shown that nasendoscopy is made easier with the use of lubrication at the expense of the quality of the view obtained, but had no effect on the discomfort or pain experienced by the patient. We set out to determine whether the advantages of lubrication with a standard lubricant (KY Jelly) could be achieved by using water, without incurring the same disadvantages.

DESIGN

Single blind randomized controlled trial.

SETTING

Outpatient Departments at two District General Hospitals.

PARTICIPANTS

One hundred and fifty participants selected sequentially from patients requiring a nasendoscopy where the endoscope would be passed far enough to view the larynx. Patients requiring topical anaesthetic were excluded.

METHODS

Patients were randomly assigned to have either water or standard lubricant applied to the nasendosope prior to nasendoscopy. Levels of pain experienced by the patient were recorded on a visual analogue score as well as visual analogue scores from the clinician for the levels of difficulty in passing the endoscope. All participants who were entered the study completed the study. Endoscopy was performed by all grades of medical staff.

MAIN OUTCOME MEASURES

Levels of pain experienced by the participants were assessed by a visual analogue scale. Difficulty of passing the scope was indicated by the endoscopist using a visual analogue scale, as was the quality of image obtained.

RESULTS

Endoscopists found the insertion of the endoscope was easier and the image better when water was used rather than KY Jelly. There was no significant difference in reported in levels of pain experienced by the patient.

CONCLUSION

Although the use of water as a lubricant during nasendoscopy confers no additional benefit in term of the levels of pain suffered by patients during the procedure, it makes the insertion of the endoscope easier and provides a better quality image than standard lubrication.

A Double-Blind Randomized Placebo-Controlled Pilot Study Comparing Topical Immunomodulating Agents and Corticosteroids for Treatment of Experimentally Induced Nickel Contact Dermatitis

BACKGROUND

Although topical glucocorticoids are effective for most inflammatory skin disorders, their use is limited by local and systemic side effects. Tacrolimus and pimecrolimus are immunomodulators that provide clinicians with steroid-sparing options in the long-term topical treatment of allergic contact dermatitis.

OBJECTIVE

To obtain pilot data regarding the relative efficacies of pimecrolimus 1% cream, tacrolimus 0.1% ointment, clobetasol propionate 0.05% ointment, and triamcinolone acetonide 0.1% ointment, as compared to control preparations (Vanicream and petrolatum), for treatment of experimentally induced nickel contact dermatitis.

METHODS

Twenty-one volunteers with positive patch test reactions to nickel sulfate 5% at six sites (three on each arm) applied each study medication to one nickel site, respectively, twice daily for 14 days. Study medications were prepared in identical syringes, and the site of application was randomly assigned by a computer-generated randomization schedule. Assessments were performed at 3, 7, 10, and 14 days after randomization.

RESULTS

Most reactions were coded as resolved or as almost resolved by day 14 regardless of treatment. Although most pairwise comparisons were not statistically significant, a clear trend was observed for sites treated with active drug to do better than control sites.

CONCLUSION

Possible explanations for these results include contamination by neighboring medication sites, timing of assessments, and lack of repeated nickel applications.

Tacrolimus: a review of its use for the management of dermatoses

The newly developed immunomodulator tacrolimus (FK506) is the first of a new class of agents that have enormous potential to change the way that dermatoses are treated and managed. Tacrolimus has been found to be active in a topical formulation with the latter exerting its effects by acting on the signal transduction pathways inside T cells and inhibiting gene transcription. The result is decreased responsiveness of T cells to antigens. Percutaneous absorption of tacrolimus is higher in diseased skin as opposed to healthy skin and, therefore, the drug will be taken in at progressively lower quantities as lesions heal. There is limited systemic absorption of tacrolimus over the course of therapy. The most extensive experience with tacrolimus has been in treating atopic dermatitis. In numerous trials, tacrolimus ointment 0.03-0.3% has shown to be effective in reducing the symptoms and severity of atopic dermatitis in adults and the paediatric population. Furthermore, there have been no significant toxic effects associated with topical therapy with tacrolimus. The most common complaint is that of local irritation after applying the ointment. This is generally transient and the patient is able to continue with therapy. The other dermatoses where tacrolimus has been used include contact dermatitis, psoriasis and pyoderma gangrenosum.

Efficacy of topical corticosteroids in nickel-induced contact allergy

In this study we used the nickel contact allergy patch (CAP) test to investigate the effect of topical corticosteroids on allergic contact dermatitis (ACD). On day 1, three CAP tests were applied for 48 h on the forearms of 20 female volunteers with a known nickel ACD. CAP of the right forearm contained 5% nickel, and of the left forearm physiological saline. Clinical scoring, transepidermal water loss and skin hydration were measured on day 1 before CAP application, on day 4 (0, 2 and 6 h) after ACD and from days 5 to 8 (0 h). A topical corticosteroid and its vehicle were applied twice daily starting from day 4 on two ACD sites. Transepidermal water loss values were significantly decreased on the topical-corticosteroid-treated sites in the early phase of ACD (day 4, 6 h after the first application) while clinical efficacy showed significant improvement on days 7 and 8. The vehicle was found to improve skin hydration only on day 8. In conclusion the topical corticosteroid improved the skin barrier function in the early inflammatory phase of ACD (day 4, 6 h). The lack of improvement in transepidermal water loss in the later phase of ACD might be accounted for by the secondary effects of the corticosteroid on proliferation and differentiation of keratinocytes.

The diagnostic evaluation, treatment, and prevention of allergic contact dermatitis in the new millennium

Identifying the etiology of allergic contact dermatitis is a rewarding yet challenging endeavor. Not all allergic contact reactions are eczematous in appearance. The most reliable clinical clue to the allergic nature of the dermatitis is its geographic distribution. Once a list of culprit allergens has been identified by patch testing, the practitioner must identify the relevant allergen(s) and counsel the patient in avoidance. For most individuals, allergen avoidance results in resolution of the dermatitis; however, some patients will require continuing symptomatic therapy despite avoidance. For those patients unable to avoid known allergens, immunosuppressant therapies (including phototherapy) or barriers can be beneficial. Currently, hyposensitization is not a viable alternative for the treatment of allergic contact dermatitis.

Transcriptional activation of endogenous retroviral sequences in human epidermal keratinocytes by UVB irradiation

Ultraviolet radiation is a pathogenic factor in various diseases, e. g., autoimmune disorders such as lupus erythematosus. On the other hand, endogenous retroviruses are discussed as etiologic agents in lupus erythematosus. Therefore, we investigated the influence of ultraviolet irradiation on expression of human endogenous retroviral sequences and human endogenous retroviral sequence promoter-driven transcription of cellular genes using human epidermal keratinocytes as a model system. First, conserved sequences of endogenous retroviral pol genes were amplified from cellular mRNA by reverse transcriptase polymerase chain reaction with degenerate oligonucleotide primers. Polymerase chain reaction products were hybridized in a reverse dot blot hybridization assay to a representative number of distinct cloned human endogenous retroviral pol fragments. Using this method, we could show that irradiation with 30 mJ per cm2 ultraviolet B activates transcription of various endogenous retroviral pol sequences in primary epidermal keratinocytes as well as in a spontaneously immortalized keratinocyte cell line (HaCaT). Interestingly, some of these sequences were found to be closely related to pol sequences of human endogenous retroviral sequences which have been shown to be expressed in autoimmune patients. Analysis of human endogenous retroviral pol expression in vivo using skin biopsies of lupus erythematosus patients revealed similar activation patterns. In a second approach, ultraviolet B- induced chimeric transcripts were isolated which are initiated by human endogenous retroviral promoters and proceed into cellular sequences using a newly established modified differential display polymerase chain reaction technique. The activation of human endogenous retroviral sequence transcription by ultraviolet B may contribute to the pathogenesis of lupus erythematosus, where inappropriate antigenic presentation of ultraviolet B-induced viral and cellular proteins could stimulate autoantibody production.

A macrolactam inhibitor of T helper type 1 and T helper type 2 cytokine biosynthesis for topical treatment of inflammatory skin diseases

T lymphocytes play a critical part in inflammatory skin diseases but are targeted by available therapies that have only partial efficacy, significant side-effects, or both. Because psoriasis, atopic dermatitis, and allergic contact hypersensitivity are associated with T helper type 1 (Th1), T helper type 2 (Th2), or mixed Th1-Th2 cell subsets and cytokine types, respectively, there is a need for a better broad-based inhibitor. The macrolactam ascomycin analog, ABT-281, was found to inhibit potently T cell function across species and to inhibit expression of multiple cytokines in human peripheral blood leukocytes which have been found in human skin disease cells and tissues. These included immunoregulatory Th1 (interleukin-2 and interferon-gamma) and Th2 (interleukin-4 and interleukin-5) cytokines. ABT-281 was shown to have potent topical activity (ED50 = 0.6% in acetone/olive oil) in a stringent swine model of allergic contact hypersensitivity, but its potency was markedly reduced compared with ascomycin when administered systemically due to more rapid clearance. Topical application of 3% ABT-281 in acetone/olive oil over 25% of the body surface in swine resulted in undetectable blood levels. Compared with a wide potency range of topical corticosteroids in clinical formulations, 0.3% and 1% ABT-281 ointments profoundly inhibited dinitrochlorobenzene-induced contact hypersensitivity in the pig by 78% and 90%, respectively, whereas super-potent steroids such as clobetasol propionate only inhibited in the 50% range and mild to moderate potency steroids such as fluocinolone acetonide were inactive. The potent topical activity of ABT-281 in swine, its superior efficacy, its rapid systemic clearance following uptake into the bloodstream, and its ability to inhibit cytokine biosynthesis of both Th1 and Th2 cell subsets, suggests that it will have a broad therapeutic value in inflammatory skin diseases, including psoriasis, atopic dermatitis, and allergic contact dermatitis.

Successful treatment of Schamberg's disease with pentoxifylline

Three patients with Schamberg's disease were treated with pentoxifylline, 300 mg daily for 8 weeks. A significant response was observed within 2 to 3 weeks. One patient had recurrence after discontinuation of this treatment; but promptly responded to resumption of therapy. No adverse effects were noted in any patients. We investigated the expression pattern of adhesion molecules in relation to perivascular accumulation of lymphocytes in specimens obtained before and after treatment with pentoxifylline in these patients. Our results suggest that pentoxifylline exerts its therapeutic effects on Schamberg's disease at the level of T-cell adherence to endothelial cells and keratinocytes.

Ultraviolet B and H2O2 are potent inducers of vascular endothelial growth factor expression in cultured keratinocytes

Vascular endothelial growth factor (VEGF), also known as vascular permeability factor, is strongly expressed by epidermal keratinocytes during wound healing, in psoriasis, and in bullous diseases such as erythema multiforme and bullous pemphigoid. All of these disorders are characterized by increased microvascular permeability and angiogenesis. Since the development of erythema as a result of hyperpermeable blood vessels is also a common feature after excess sun exposure, we speculated about an up-regulation of VEGF expression by ultraviolet (UV) light. To test this hypothesis, we analyzed the effect of UVB irradiation on VEGF expression in cultured keratinocytes. Thereby we found a large increase in VEGF mRNA and protein levels upon irradiation of quiescent keratinocytes with sublethal and physiologically relevant doses of UVB. Although H2O2 was also a potent inducer of VEGF expression, the effect of UVB irradiation is unlikely to be mediated by reactive oxygen species as determined by the use of antioxidants. Further experiments revealed that the UVB-induced overexpression of VEGF is dependent on de novo protein synthesis and might occur via release of soluble mediators, which subsequently turn on VEGF expression. In summary, our results suggest a novel role of VEGF in the induction of erythema after excess sun exposure.

Epidermal cytokines in allergic contact dermatitis

The understanding of cutaneous immunology has grown significantly during the past decade, particularly regarding the immune function of keratinocytes. Keratinocytes play a major role in immune and inflammatory reactions, mainly through synthesis and release of cytokines. The cytokine network in the skin is an important contributor to normal homeostasis and to the pathogenesis of cutaneous disease. Although cytokine dysregulation has been implicated in the pathogenesis of many cutaneous diseases, allergic contact dermatitis is one that has been the most extensively studied. The aim of this article is to provide a comprehensive current review of the mechanisms of allergic contact dermatitis with particular emphasis on the role of epidermal cytokines.