Tacrolimus (FK506): new treatment approach in superantigen-associated diseases like atopic dermatitis?

Staphylococcus aureus from Atopic Dermatitis Patients: Its Genetic Structure and Susceptibility to Phototreatment

We characterized the population of Staphylococcus aureus from patients with atopic dermatitis (AD) in terms of (i) genetic diversity, (ii) presence and functionality of genes encoding important virulence factors: staphylococcal enterotoxins (sea, seb, sec, sed), toxic shock syndrome 1 toxin (tsst-1), and Panton-Valentine leukocidin (lukS/lukF-PV) by spa typing, PCR, drug resistance profile determination, and Western blot. We then subjected the studied population of S. aureus to photoinactivation based on a light-activated compound called rose bengal (RB) to verify photoinactivation as an approach to effectively kill toxin-producing S. aureus. We have obtained 43 different spa types that can be grouped into 12 clusters, indicating for the first-time clonal complex (CC) 7 as the most widespread. A total of 65% of the tested isolates had at least one gene encoding the tested virulence factor, but their distribution differed between the group of children and adults, and between patients with AD and the control group without atopy. We detected a 3.5% frequency of methicillin-resistant strains (MRSA) and no other multidrug resistance. Despite genetic diversity and production of various toxins, all isolates tested were effectively photoinactivated (bacterial cell viability reduction ≥ 3 log10 units) under safe conditions for the human keratinocyte cell line, which indicates that photoinactivation can be a good option in skin decolonization. IMPORTANCE Staphylococcus aureus massively colonizes the skin of patients with atopic dermatitis (AD). It is worth noting that the frequency of detection of multidrug-resistant S. aureus (MRSA) in AD patients is higher than the healthy population, which makes treatment much more difficult. Information about the specific genetic background of S. aureus accompanying and/or causing exacerbations of AD is of great importance from the point of view of epidemiological investigations and the development of possible treatment options.

Mechanistic insights into topical tacrolimus for the treatment of atopic dermatitis

More than 15 years have passed since the clinical launch of topical tacrolimus for the treatment of atopic dermatitis. Its efficacy and safety have been clearly demonstrated in many global and domestic short-term and long-term clinical trials. Although the prolonged external application of steroids causes many adverse reactions including cutaneous atrophy, no such reactions occur with the use of topical tacrolimus. Therefore, the therapeutic guidelines recommend a combined topical treatment with tacrolimus and steroids. Tacrolimus is a potent immunosuppressant. However, recent studies have revealed its diverse action on the cardinal pathomechanisms of atopic dermatitis. In this review, we summarize the mechanistic role of tacrolimus in various aspects of allergic inflammation including mast cell activation, innate allergic response, pruritus, sensory nerve activation, and skin barrier dysfunction.

Atopic dermatitis management with tacrolimus ointment (Protopic®)

Tacrolimus ointment is the first of a new class of non-steroidal topical immunomodulators indicated for the treatment of atopic dermatitis. Topical tacrolimushas been subject to an extensive clinical development program involving more than 16,000 patients. A clinical trial program, including vehicle-controlled studies, short- and long-term comparative studies and long-term safety studies, has investigated tacrolimus 0.1%and 0.03%ointment for the treatment of atopic dermatitis in adults and children aged 24 months and older. Tacrolimusmonotherapy is rapidly effective, resulting in clinical improvements within three days of starting therapy, and produces a progressive increase in efficacy that is sustained during long-term treatment. Tacrolimus treats the signs and symptoms of atopic dermatitis, reduces the incidence of flares, and offers the potential for long-term disease control. No major safety concerns have been reported to date. Tacrolimusointment is generally well tolerated, the primary adverse events being mild to moderate and transient application-site reactions: skin burning, pruritus and erythema. Tacrolimus oint-ment is a significant advance in dermatology and provides physicians with an alternative to conventional topical corticosteroid therapy.

Atopic dermatitis: a practice parameter update 2012

This parameter was developed by the Joint Task Force on Practice Parameters, representing the American Academy of Allergy, Asthma & Immunology (AAAAI); the American College of Allergy, Asthma & Immunology (ACAAI); and the Joint Council of Allergy, Asthma and Immunology. The AAAAI and the ACAAI have jointly accepted responsibility for establishing "Atopic dermatitis: a practice parameter update 2012." This is a complete and comprehensive document at the current time. The medical environment is a changing environment, and not all recommendations will be appropriate for all patients. Because this document incorporated the efforts of many participants, no single individual, including those who served on the Joint Task Force, is authorized to provide an official AAAAI or ACAAI interpretation of these practice parameters. Any request for information about or an interpretation of these practice parameters by the AAAAI or ACAAI should be directed to the Executive Offices of the AAAAI, the ACAAI, and the Joint Council of Allergy, Asthma & Immunology. These parameters are not designed for use by pharmaceutical companies in drug promotion. Published practice parameters of the Joint Task Force on Practice Parameters for Allergy & Immunology are available online at http://www.jcaai.org.

The role of Staphylococcal enterotoxin in atopic keratoconjunctivitis and corneal ulceration

BACKGROUND

Patients with atopic eczema frequently experience colonization with Staphylococcus aureus that is directly correlated with the eczema severity. We hypothesized that S. aureus-secreted enterotoxins (SE) are involved in the pathophysiology of atopic keratoconjunctivitis (AKC).

METHODS

A total of 45 subjects (18 with AKC, nine vernal keratoconjunctivitis (VKC), eight seasonal allergic conjunctivitis (SAC), and ten healthy volunteers) were enrolled. Slit lamp examinations, including fluorescein staining, were performed. Scraped samples were collected from the upper tarsal conjunctiva, lower conjunctival sacs, and the skin around the eyelid margins. Superantigen (SAg) genes were detected using polymerase chain reaction (PCR).

RESULTS

Among 45 cases, S. aureus was detected significantly more in AKC patients than VKC patients (P = 0.026), SAC patients (P = 0.0003), and healthy volunteers (P = 0.0001). SAg genes were detected in 11 patients. SEB (2/11), SEG (8/11), and SEI (8/11) were detected, but no other SE. There was a significant difference in SE detection between AKC and SAC patients (P = 0.03). In severe types of ocular allergic disease such as AKC and VKC (N = 27), SE was detected in six of ten patients with corneal ulcers and two of 17 patients without corneal ulcers. SE was detected in significantly more patients with corneal ulcers (P = 0.025).

CONCLUSIONS

In patients with AKC, S. aureus and SE were detected more frequently compared with other patients and healthy volunteers, especially in association with corneal ulceration suggesting a role of SE. So far, it is unknown whether SE leads to tissue damage of the cornea by initiating an immune response or has direct toxic effects.

The impact of tacrolimus on the immunopathogenesis of staphylococcal enterotoxin-induced systemic inflammatory response syndrome and pneumonia

Staphylococcal superantigens (SAg) are a family of potent exotoxins produced by Staphylococcus aureus. They play an important role in the pathogenesis of staphylococcal shock and pneumonia by causing a robust activation of the immune system and eliciting a strong surge in systemic cytokine and chemokine levels. Given the biological functions of SAg, we evaluated the efficacy of tacrolimus, a potent immunosuppressive agent, in the prophylaxis and therapy of staphylococcal TSS and pneumonia using human leukocyte antigen (HLA)-DR3 transgenic mice. Tacrolimus significantly inhibited staphylococcal SAg induced T cell activation in vitro. In vivo, tacrolimus significantly suppressed the SAg-induced elevation in serum cytokine and chemokine levels when given prophylactically, when administered immediately or even 2 h following systemic SAg challenge. Paradoxically, neither the prophylactic nor post-exposure treatment with tacrolimus protected mice from lethal SAg-induced TSS. A closer examination revealed that tacrolimus failed to suppress SAg-induced T cell proliferation and systemic pathology, including gut dysfunction. Tacrolimus also failed to protect from lethal pneumonia induced by a SAg-producing S. aureus strain. Thus, our study showed that even though T cell activation by SAg plays a major role in the immunopathogenesis of TSS and pneumonia, tacrolimus alone has no beneficial effect.

Does allergy impair innate immunity? Leads and lessons from atopic dermatitis

Host defence responses against invading pathogens are well-balanced, inflammatory processes of the innate and adaptive immune system. Impaired development or abnormal function of either system can result in failure to control pathogens and to clear infections. Infections have been claimed to modulate the onset and course of allergic diseases. This so-called hygiene hypothesis is still an active area of research. In contrast, the effects of allergies on infections and pathogen-directed immune responses are less well understood. Here, we have reviewed the existing evidence that allergies result in impaired innate immunity and we discuss recent observations that may explain why and how innate immunity is dysfunctional in allergic patients. With a focus on atopic dermatitis as a model of allergic disease, we speculate that one of the key features of allergic conditions, namely Th2 polarization, leads to several independent inhibitory effects on host defence and consequently to a higher risk of infections in allergic patients. A better understanding of impaired host defence and its mechanisms in allergic subjects will help to improve the management of these diseases.

New visions for atopic eczema: an iPAC summary and future trends

Atopic eczema (AE) is a chronic inflammatory skin disease characterized by pruritus, dry skin and an ongoing course of exacerbations and remissions. AE is a common disorder in children with a worldwide cumulative prevalence of 15-20% in this age group. AE has a strong familial predisposition. While AE is a complex disease with multiple gene involvement, recent interest has focused on genes involved in skin barrier/epidermal differentiation and in immune response/host defense. Recent developments and future directions on pathogenesis, diagnosis, natural course and prognosis are discussed.

Role of bacterial pathogens in atopic dermatitis

The skin of atopic dermatitis (AD) patients exhibits a striking susceptibility to colonization and infection with Staphylococcus aureus. This review summarizes our understanding about the role of S. aureus in AD. Indeed, S. aureus colonization is both a cause and a consequence of allergic skin inflammation. The mechanisms that allergic skin inflammation of AD promotes the increase of S. aureus colonization include skin barrier dysfunction, increased synthesis of the extracellular matrix adhesins for S. aureus, and defective innate immune responses due to decreased production of endogenous antimicrobial peptides. On the other hand, the exotoxins secreted by S. aureus are superantigens. Staphylococcal superantigens (SsAgs) may penetrate the skin barrier and contribute to the persistence and exacerbation of allergic skin inflammation in AD through the stimulation of massive T cells, the role of allergens, direct stimulation of antigen-presenting cells and keratinocytes, the expansion of skin-homing cutaneous lymphocyte-associated antigen-positive T cells, and the augmentation of allergen-induced skin inflammation. SsAgs also induce corticosteroid resistance. In therapeutic interventions, anti-inflammatory therapy alone is very effective in reducing S. aureus colonization on the skin, but antibiotic treatment alone is unable to improve the allergic skin inflammation of AD. Therefore, we recommend the combination therapy of anti-inflammatory drugs and antibiotics in the AD patients with secondary bacterial infection, exacerbated AD, or poorly controlled AD. However, when AD is well controlled by anti-inflammatory drugs alone, we do not recommend the antibiotic therapy.

Systemic ciclosporin and tacrolimus in dermatology

Ciclosporin and tacrolimus are calcineurin inhibiting immunosuppressant agents useful in the treatment of immune-mediated inflammatory dermatoses. Available data and clinical experience demonstrate ciclosporin's efficacy in treating psoriasis, atopic dermatitis, pyoderma gangrenosum, lichen planus, autoimmune bullous disease (in combination with corticosteroids), recalcitrant chronic idiopathic urticaria, and chronic dermatitis of the hands and feet. Although the role of topical tacrolimus in atopic dermatitis is well established, such experience with the oral formulation of tacrolimus has been limited. However, there are several case studies and anecdotal reports of the successful use of oral tacrolimus in various dermatoses. In this article we discuss the utility of systemic ciclosporin and tacrolimus in dermatology.

Gamma-globulin inhibits superantigen-induced lymphocyte proliferation and cytokine production

BACKGROUND

High-dose pooled human immunoglobulin (PHIG) treatment is sometimes effective in superantigen related inflammatory diseases, such as toxic shock syndrome and Kawasaki disease. Neutralizing antibody to superantigen might provide protection, but antigen independent immune regulation of PHIG is also a proposed mechanism.

METHODS

Staphylococcal enterotoxin B (SEB)-specific IgG antibody in PHIG products (Venoglobulin IH(R)) was detected by ELISA. The suppressive effect of PHIG or its fragments on proliferation and cytokine (IL-4 and IFN-gamma) production from SEB-stimulated peripheral blood mononuclear cells was examined.

RESULTS

SEB-specific IgG was detected in PHIG products. PHIG (6.25-25mg/ml) suppressed SEB-induced proliferation and cytokine production in a dose-dependent manner. Fab and F (ab') 2 fractions of PHIG also suppressed the responses, but depletion of SEB-specific antibody from PHIG did not affect the inhibitory effects. The Fc fragment of PHIG also showed partial, but significant suppression.

CONCLUSIONS

These data suggested the possibility that PHIG suppressed SEB-induced proliferation and cytokine production by some mechanisms independent of the presence of neutralizing antibody.

Addition of topical pimecrolimus to once-daily mid-potent steroid confers no short-term therapeutic benefit in the treatment of severe atopic dermatitis; a randomized controlled trial

BACKGROUND

Combination therapy with pimecrolimus cream 1%, a topical calcineurin inhibitor (TCI), and fluticasone propionate cream 0.05% (FP), a mid-potency topical corticosteroid, may have a synergistic effect for treatment of atopic dermatitis (AD) because their mechanism of action differs.

OBJECTIVES

To assess the efficacy of concomitant pimecrolimus twice daily/FP once daily vs. vehicle twice daily/FP once daily in patients with severe AD.

METHODS

An exploratory, 2-week, double-blind, randomized, within-patient study was conducted (n = 45). Two target areas of similar severity, size and location were assessed. Assessments included the modified Eczema Area and Severity Index (0-12 scale) (primary variable), localized investigator global assessment (0-4 scale) and Patients' Self-Assessment of Disease Severity (0-4 scale).

RESULTS

Data for all variables were similar for the TCI/FP and vehicle/FP treatments.

CONCLUSIONS

The efficacy observed for treatment of severe AD flares with this TCI/FP combination regimen was equivalent to that of vehicle/FP.

Staphylococcus colonization in atopic dermatitis treated with fluticasone or tacrolimus with or without antibiotics

BACKGROUND

The skin of patients with atopic dermatitis (AD) exhibits a striking susceptibility to colonization and infection by Staphylococcus aureus. Treatment with topical anti-inflammatory drugs alone can reduce S. aureus colonization.

OBJECTIVES

To compare the clinical severity of AD and the S. aureus colonization rate between AD patients treated with topical glucocorticoids and those treated with tacrolimus and to evaluate the effects of complementary topical antistaphylococcal antibiotic therapy and the development of fusidic acid-resistant S. aureus.

METHODS

Sixty AD patients were enrolled in a prospective, parallel, randomized study of an 8-week treatment with topical 0.05% fluticasone propionate or 0.03% tacrolimus, with or without complementary fusidic acid. Disease severity scoring of AD based on SCORing of Atopic Dermatitis (SCORAD), colonization rate and density of S. aureus on the skin, and antibiotic susceptibility of S. aureus isolates were evaluated.

RESULTS

The reduction in SCORAD scores correlated with the reduction of S. aureus numbers. Treatment with topical tacrolimus resulted in a comparable reduction in SCORAD scores to fluticasone but a slower eradication of S. aureus. Complementary fusidic acid had no additional benefit compared with fluticasone or tacrolimus alone. Two patients developed fusidic acid-resistant S. aureus after 8 weeks of fusidic acid treatment.

CONCLUSION

Tacrolimus is an appropriate alternative treatment for chronic AD. Topical anti-inflammatory therapy alone to improve the allergic skin inflammation of AD can reduce S. aureus colonization of the skin. Topical antibiotics should be reserved for short-term use in obvious secondary bacterial infection.

Atopic dermatitis

Atopic dermatitis is an especially common and frustrating condition, and the prevalence is increasing. The disease can adversely affect the quality of life of patients and caregivers. Significant advances in our understanding of the pathogenesis have led to improvements in therapy. Patient and caregiver education, avoidance of potential triggering factors, optimal skin care, and pharmacotherapy offer the potential for good control for most patients.

Diagnosis and treatment of atopic dermatitis in children and adults: European Academy of Allergology and Clinical Immunology/American Academy of Allergy, Asthma and Immunology/PRACTALL Consensus Report

There are remarkable differences in the diagnostic and therapeutic management of atopic dermatitis practiced by dermatologists and pediatricians in different countries. Therefore, the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology nominated expert teams who were given the task of finding a consensus to serve as a guideline for clinical practice in Europe as well as in North America. The consensus report is part of the PRACTALL initiative, which is endorsed by both academies.

Safety and efficacy of topical calcineurin inhibitors in the treatment of childhood atopic dermatitis

Approximately 10-20% of infants in industrialized countries experience atopic dermatitis. In recent decades topical corticosteroids have been the first-choice therapy for treatment of flares. However, this form of therapy may induce skin atrophy, especially after application to facial lesions or with long-term use. Thus, development of new anti-inflammatory topical agents for the treatment of childhood atopic dermatitis was needed. The topical calcineurin inhibitors tacrolimus and pimecrolimus have an effect on various cells of the cutaneous immune system, specifically on T cells, by inhibiting the phosphatase calcineurin and preventing the transcription of proinflammatory cytokines. In several clinical studies of children and adults with atopic dermatitis, topical calcineurin inhibitors were found to be effective both on the face and the trunk and extremities, in both short- and long-term treatment regimens. Tachyphylaxis or rebound were not observed. In most patients an improvement of their eczema occurred during the first week of treatment, as measured by subjective and objective clinical signs of atopic dermatitis. Treatment significantly reduced the incidence of flares and the need for corticosteroids in children and adults. Treatment success, commonly defined as 'excellent improvement' or 'clearing of all lesions', was observed in more than one-third of all children treated with 0.03% or 0.1% tacrolimus or 1% pimecrolimus. Topical application of pimecrolimus and tacrolimus does not lead to significant blood concentrations of these agents in the majority of children with atopic dermatitis, and any increase in blood concentrations decreases after a few days of therapy. No changes in laboratory parameters were observed in short- and long-term studies in patients with atopic dermatitis. The most common adverse effect following the application of topical calcineurin inhibitors is mild to moderate symptoms of irritation such as burning, erythema and pruritus, which occurred in up to 20% of all children treated with tacrolimus and 10% of children treated with pimecrolimus, and usually faded after a few days. In contrast to topical corticosteroids, calcineurin inhibitors do not induce skin atrophy, even after long-term use. Topical calcineurin inhibitors have been proven to be effective and have a good safety profile during short-term and long-term use for up to 1 year with pimecrolimus and up to 4 years with tacrolimus. Given the lack of extensive experience with use of topical calcineurin inhibitors over longer periods, regular use of these agents, particularly in children, should be undertaken only after careful consideration of individual cases. Sun protection should also be advised.

Secondary infections in patients with atopic dermatitis

Clinicians have long since been aware that bacteria and other microorganisms play a role in the etiology of atopic dermatitis. Indeed, the immunological profile of atopy favors colonization by Staphylococcus aureus, and the bacteria are present in most patients with atopic dermatitis, even in the absence of skin lesions. Clinical signs of impetiginization, such as weeping and crusting, periauricular fissuration, or small superficial pustules are a sensitive indicator that the numbers of S. aureus may have increased and a clinical indication of secondary infected dermatitis. However, recent research that has focussed on the role of S. aureus in atopic dermatitis, offers a reversed perspective, by presenting evidence that the underlying pathology of atopic dermatitis, i.e. an alteration of the skin barrier and inflammation of the upper dermis, depends itself on the presence of an infectious process. In other words, secondary infection with S. aureus emerges as a cause of atopic dermatitis. Secondary infections due to fungi have, comparatively, received less attention, but there is evidence for a role for Malassezia spp. as a factor in dermatitis with a head and neck distribution pattern. Viral infections, such as herpes simplex virus, and mixed infections of intertriginous spaces, may complicate an underlying atopic dermatitis, but are not perceived as etiologic factors. Recent research has greatly contributed to our understanding of the pathophysiological potential of S.aureus superantigens in atopic dermatitis, suggesting that antibiotic therapy might be an important element in the therapeutic management of atopic dermatitis. At present, however, the clinical evidence is scarce with regards to demonstrating a clear advantage of combined anti-inflammatory and antibiotic treatment, compared with anti-inflammatory treatment alone. If there is a consensus that the presence of clinically infected lesions in atopic dermatitis warrants a course of specific antibiotic topical therapy, the clinical benefit of antibiotic agents in apparently uninfected atopic dermatitis, as present in the majority of patients, remains an open question.Moreover, the impact of adjuvant skin care on the cutaneous microflora needs to be quantified in order to properly assess the role of specific antibiotic therapy in clinically uninfected atopic dermatitis. In the meantime, secondary infections in atopic dermatitis remain a secondary problem in clinical atopic dermatitis management, and specific anti-infective therapy remains a method of fine-tuning for optimizing individual atopic dermatitis treatment.

Expression of glucocorticoid resistance following social stress requires a second signal

Stimulation of splenocytes from socially stressed mice [social disruption (SDR)] with Gram-negative bacterial lipopolysaccharide (LPS) revealed a state of functional glucocorticoid (GC) resistance. LPS-stimulated splenocytes were less sensitive to the inhibitory effects of corticosterone. This study demonstrated that activation signals were required for the expression of splenic GC resistance. The results demonstrated that six cycles of SDR induced splenomegaly and increased the number of CD11b-positive monocytes. SDR also increased the viability of cultured, nonstimulated splenocytes, and addition of corticosterone reduced the viability of these cells in a dose-dependent manner. However, following stimulation with LPS, the sensitivity of SDR splenocytes to GC was reduced. Similar results were obtained using lipid A, a fraction of the LPS molecule that binds to Toll-like receptor (TLR)4. Furthermore, C3H/HeJ mice that do not possess a functional TLR4 molecule responded to SDR with an increased number of CD11b-positive monocytes in the spleen and increased viability of nonstimulated splenocytes. However, neither LPS nor lipid A stimulation resulted in the expression of GC resistance. Together, these findings suggest that the expression of GC resistance in response to SDR requires a second signal that can be provided by ligation of TLR4.

Infection in atopic dermatitis

PURPOSE OF REVIEW

Atopic dermatitis is a chronic inflammatory skin disease commonly seen in children, but it also occurs in adults. This skin disease is often triggered by bacterial, fungal, or viral skin infections. The mechanisms resulting in this increased propensity for skin infections have been an area of active investigation.

RECENT FINDINGS

Recent studies suggest that the skin of patients with atopic dermatitis has increased avidity for binding to Staphylococcus aureus and is deficient in its ability to generate antimicrobial peptides needed to eradicate infectious agents.

SUMMARY

The current review will examine recent literature on the etiology and pathogenesis of infection in atopic dermatitis. These observations are likely to have importance implications for management of atopic dermatitis.

[Practice experience with topical calcineurin inhibitors]

The clinical experience with topical calcineurin inhibitors in the field is still rudimentary, if compared to our knowledge of topical corticosteroids. This is especially true for the long-term effects. The systemic transcutaneous absorption that occurs during the therapy of atopic dermatitis is quantitatively irrelevant. However, in the setting of permanent disruption of the skin barrier, as may be encountered in rare Genodermatoses, but as well in cases that do not respond to therapy, continued treatment my result in clinically relevant blood levels. Side effects of topical calcineurin inhibitors may be separated into two groups, i.e. local intolerance reactions, and skin infections. While the typical burning sensation of the newly treated skin is ephemeral, local alcohol intolerance, albeit less frequent, will persist throughout the treatment period. Regarding skin infections, Eczema herpeticatum seems to be the only serious complication; adequate preventive will further reduce the risk of this rare complication.

Advances in allergic skin diseases

During the past year there have been significant advances in our understanding of the mechanisms underlying allergic skin diseases. This article reviews some of these advances in atopic dermatitis and urticaria. The introduction of a new class of topical anti-inflammatory medications, topical calcineurin inhibitors, has significantly increased our treatment options and led to a rethinking of potential management approaches in atopic dermatitis.

Tacrolimus ointment for the treatment of atopic dermatitis is not associated with an increase in cutaneous infections

OBJECTIVE

The purpose of this study was to evaluate the risk of cutaneous infection in patients with atopic dermatitis treated with tacrolimus ointment.

METHODS

Data for 1554 patients with atopic dermatitis, treated with tacrolimus ointment in 5 clinical trials, were analyzed.

RESULTS

In 3 controlled studies, the 12-week adjusted incidence of all cutaneous infections in patients treated with the vehicle, 0.03%, and 0.1% tacrolimus ointment, respectively, was 18.0%, 24.8%, and 17.7% for adult patients, and 20.9%, 19.6%, and 23.6% for pediatric patients. The incidence of any individual cutaneous infection was not significantly higher in the tacrolimus group than in the vehicle group, with the exception of folliculitis in adults. In two open-label studies, there was no evidence of an increased risk of cutaneous infections with long-term use of 0.1% tacrolimus ointment (up to 1 year), based on the incidence of adverse events, incidence by cumulative length of exposure, or hazard rates.

CONCLUSION

Treatment with tacrolimus ointment (0.03% or 0.1%) does not increase the risk of cutaneous bacterial, viral, or fungal infections in patients with atopic dermatitis.

Topical noncorticosteroid immunomodulation in the treatment of atopic dermatitis

At present, the first-line drugs for treating atopic dermatitis are topical corticosteroids. They are effective when used short-term; however, long-term use of the corticosteroids is associated with suppressive effects on the connective tissue, seen as skin atrophy or resistance to therapy. Currently, two topical noncorticosteroid immunomodulators tacrolimus (FK506) and pimecrolimus (SDZ ASM 981) are under development, or already on the market in some countries for atopic dermatitis. These two compounds show structural similarity. In T lymphocytes they bind to the same cellular receptor, the FK-binding protein (FKBP) or macrophilin-12. Tacrolimus shows a 3-fold greater affinity to FKBP compared with pimecrolimus. The tacrolimus/ pimecrolimus-FKBP complex further binds to calcineurin, an enzyme vital for the early activation of T cells. The consequence of calcineurin binding is a lack of activation of both T helper cell types 1 and 2. Further effects of these compounds have been suggested on other inflammatory cells, such as Langerhans cells and mast cells/basophils. In contrast to corticosteroids, no suppressive effects on connective tissue cells have been observed. Taken together, treatment of inflammation results in healing of the barrier function of the skin. This again results in reduced bioavailability of the drug, as compared with systemic use. Placebo-controlled studies have shown the efficacy of both tacrolimus (at 0.03 and 0.1%) and pimecrolimus (at 0.6 and 1%). The main adverse event in these studies has been a burning sensation and increased pruritus at the site of application. Typically, these adverse events are observed only during the first days of treatment. Long-term safety studies, of up to one year, have not revealed any new adverse events. So far, long-term use of topical noncorticosteroid compounds has not been associated with signs of immune deficiency. Although there is currently no evidence for clinically relevant, prolonged adverse effects, some of these, such as an increased risk of photocarcinogenesis, need to be monitored. There is evidence from tacrolimus studies that monotherapy results in better long-term results when compared with combination therapy with corticosteroids. Tacrolimus and pimecrolimus could replace topical corticosteroids as the first-line treatment of atopic dermatitis.

Tacrolimus enhances irritation in a 5-day human irritancy in vivo model

Tacrolimus (FK 506) is a macrolide discovered in 1984 as a metabolic product of Streptomyces tsukabaensis. It has been used successfully in treating atopic dermatitis, allergic contact dermatitis, lichen planus mucosae and pyoderma gangrenosum. In the present study, we evaluated the anti-inflammatory activity of FK 506 in 2 human skin inflammation models. FK 506 as Protopic(R) cream was tested (i) in a 4-day repetitive irritation test with 2 x daily application of sodium lauryl sulphate (SLS), and (ii) in a UVB erythema model. The effect was evaluated visually and quantified by non-invasive bioengineering methods, namely chromametry and tewametry (TEWL). When FK 506 was applied 30 min after SLS irritation, an increased inflammation in comparison to controls was observed with all 3 methods, with only the TEWL data reaching statistical significance. 1 x daily application of FK 506 for 5 days, starting at the end of the 4-day irritation period, was without any effect. Similarly, no effect of FK 506 was seen in the UVB model. In conclusion, FK 506 was shown to enhance experimentally induced irritant contact dermatitis and not to accelerate healing of irritant contact dermatitis and UVB erythema.

Pathophysiologic mechanisms in atopic dermatitis

Atopic dermatitis is a common, chronic inflammatory skin disease that frequently predates the development of asthma and/or allergic rhinoconjunctivitis. Recent studies have provided new insights into how the complex interrelationship of genetic, environmental, and immunologic factors may contribute to the development of atopic dermatitis. This article examines some of the factors involved in chronic cutaneous inflammation in this disease. Greater understanding of the mechanisms that underlie the pathophysiology of atopic dermatitis may lead to improved treatment strategies for this increasingly common skin disease.