Anti-inflammatory effect of FK-506 on human skin mast cells

Dual effect of tacrolimus on mast cell-mediated allergy and inflammation through Mas-related G protein-coupled receptor X2

BACKGROUND

Topical tacrolimus, although widely used in the treatment of dermatoses, presents with an immediate irritation on initial application resembling a pseudo-allergic reaction. Mas-related G protein-coupled receptor X2 (MRGPRX2) in mast cells (MCs) mediates drug-induced pseudo-allergic reaction and immunoglobulin E (IgE)-independent pruritis in chronic skin diseases. However, the immunosuppression mechanism of tacrolimus on MCs via MRGPRX2 has not been reported.

OBJECTIVE

To investigate the role of MRGPRX2 and the mechanism of action of tacrolimus on its short-term and long-term applications.

METHODS

Wild-type mice, KitW-sh/W-sh mice, and MrgprB2-deficient (MUT) mice were used to study the effect of tacrolimus on in vivo anaphylaxis model. LAD2 cells and MRGPRX2-knockdown LAD2 cells were specifically used to derive the associated mechanism of the tacrolimus effect.

RESULTS

Short-term application of tacrolimus triggers IgE-independent activation of MCs via MRGPRX2/B2 in both in vivo and in vitro experiments. Tacrolimus binds to MRGPRX2, which was verified by fluorescently labeled tacrolimus in cells. On long-term treatment with tacrolimus, the initial allergic reaction fades away corresponding with the downregulation of MRGPRX2, which leads to decreased release of inflammatory cytokines (P < 0.05 to P < 0.001).

CONCLUSION

Short-term treatment with tacrolimus induces pseudo-allergic reaction via MRGPRX2/B2 in MCs, whereas long-term treatment downregulates expression of MRGPRX2/B2, which may contribute to its potent immunosuppressive effect in the treatment of various skin diseases.

Shedding light on key pharmacological knowledge and strategies for pediatric atopic dermatitis

INTRODUCTION

Atopic dermatitis (AD) is an inflammatory disease affecting over 20% of the pediatric population, with 85% of cases presenting before the age of five. Recently, therapeutic options in pediatric patients have evolved rapidly, following extensive development in adult treatments.

AREAS COVERED

This review will encompass relevant molecular drivers, along with an overlook on treatment modalities in pediatric AD, as well as a summary of pipeline treatments in clinical trials for pediatric patients from PubMed, Google Scholar, and Clinicaltrials.gov up to July 2022. Topical corticosteroids are the mainstay for AD flares in adults and children. Topical approved agents in pediatric AD are calcineurin inhibitors, crisaborolecrisaborole, and ruxolitinib. Dupilumab is the only FDA approved biologic for patients with AD from six months of age. A Janus kinase inhibitor, upadacitinib, is a systemic treatment approved for pediatric AD patients (age >12 years). Systemic immunosuppressants used in pediatric AD include methotrexate, azathioprine, cyclosporinecyclosporine, and mycophenolate mofetil.

EXPERT OPINION

Data regarding disease prevention are conflicting, however, an abundance of research has transpired regarding amelioration of symptoms and induction of disease clearance by targeting numerous pathological mechanisms. Understanding the pediatric AD phenotype will further advance the field and the development of improved therapeutics.

Prescription Patterns of Topical Medications in Patients with Atopic Dermatitis: An Investigative Review Using Big Data from the National Health Insurance Corporation

BACKGROUND

Topical medications play a crucial role in the treatment of atopic dermatitis (AD). Topical corticosteroids (TCSs) remain the main treatment of choice and topical antibiotics have also been used. However, with the new topical calcineurin inhibitors (TCIs), the prescription patterns of topical agents have changed over time.

OBJECTIVE

To characterize the prescription patterns of topical medications in Korean patients with AD.

METHODS

We investigated topical medications prescribed to Korean patients with AD using the National Health Insurance Sharing System (NHISS) database over a 14-year period (2002~2015). Additionally, the potency of prescribed TCSs was compared with AD and psoriasis patients.

RESULTS

The annual prescription of TCSs showed a slightly decreasing trend without significant change. In particular, in terms of steroid class, prescription of moderate-to-low potency TCSs were increased and the use of high potency TCSs were decreased. TCSs were the most commonly prescribed topical medications for AD. Tertiary hospitals had a higher prescription rate for TCIs than secondary or primary hospitals (16.2%, 3.1%, and 1.9%, respectively). Additionally, dermatologists prescribed TCIs more frequently than pediatricians and internists (4.3%, 1.2%, and 0.6%, respectively). Among TCSs, Class 5 was prescribed the most (40.6%) followed by Class 7, 6, 4, 3, 1, and 2. When we compared the potency of TCSs prescribed for AD with psoriasis patients, moderate-to-low-potency TCSs were more commonly prescribed in AD.

CONCLUSION

Prescription patterns of topical medications had changed from 2002 to 2015 and differed according to the type of institution and specialty of the physician.

Targeting Mast Cells in Allergic Disease: Current Therapies and Drug Repurposing

The incidence of allergic disease has grown tremendously in the past three generations. While current treatments are effective for some, there is considerable unmet need. Mast cells are critical effectors of allergic inflammation. Their secreted mediators and the receptors for these mediators have long been the target of allergy therapy. Recent drugs have moved a step earlier in mast cell activation, blocking IgE, IL-4, and IL-13 interactions with their receptors. In this review, we summarize the latest therapies targeting mast cells as well as new drugs in clinical trials. In addition, we offer support for repurposing FDA-approved drugs to target mast cells in new ways. With a multitude of highly selective drugs available for cancer, autoimmunity, and metabolic disorders, drug repurposing offers optimism for the future of allergy therapy.

IgG Autoantibodies Against IgE from Atopic Dermatitis Can Induce the Release of Cytokines and Proinflammatory Mediators from Basophils and Mast Cells

IgE-mediated release of proinflammatory mediators and cytokines from basophils and mast cells is a central event in allergic disorders. Several groups of investigators have demonstrated the presence of autoantibodies against IgE and/or FcεRI in patients with chronic spontaneous urticaria. By contrast, the prevalence and functional activity of anti-IgE autoantibodies in atopic dermatitis (AD) are largely unknown. We evaluated the ability of IgG anti-IgE from patients with AD to induce the in vitro IgE-dependent activation of human basophils and skin and lung mast cells. Different preparations of IgG anti-IgE purified from patients with AD and rabbit IgG anti-IgE were compared for their triggering effects on the in vitro release of histamine and type 2 cytokines (IL-4, IL-13) from basophils and of histamine and lipid mediators (prostaglandin D₂ and cysteinyl leukotriene C₄) from human skin and lung mast cells. One preparation of human IgG anti-IgE out of six patients with AD induced histamine release from basophils, skin and lung mast cells. This preparation of human IgG anti-IgE induced the secretion of cytokines and eicosanoids from basophils and mast cells, respectively. Human monoclonal IgE was a competitive antagonist of both human and rabbit IgG anti-IgE. Human anti-IgE was more potent than rabbit anti-IgE for IL-4 and IL-13 production by basophils and histamine, prostaglandin D₂ and leukotriene C₄ release from mast cells. Functional anti-IgE autoantibodies rarely occur in patients with AD. When present, they induce the release of proinflammatory mediators and cytokines from basophils and mast cells, thereby possibly contributing to sustained IgE-dependent inflammation in at least a subset of patients with this disorder.

Dermal Delivery of the High-Molecular-Weight Drug Tacrolimus by Means of Polyglycerol-Based Nanogels

Polyglycerol-based thermoresponsive nanogels (tNGs) have been shown to have excellent skin hydration properties and to be valuable delivery systems for sustained release of drugs into skin. In this study, we compared the skin penetration of tacrolimus formulated in tNGs with a commercial 0.1% tacrolimus ointment. The penetration of the drug was investigated in ex vivo abdominal and breast skin, while different methods for skin barrier disruption were investigated to improve skin permeability or simulate inflammatory conditions with compromised skin barrier. The amount of penetrated tacrolimus was measured in skin extracts by liquid chromatography tandem-mass spectrometry (LC-MS/MS), whereas the inflammatory markers IL-6 and IL-8 were detected by enzyme-linked immunosorbent assay (ELISA). Higher amounts of tacrolimus penetrated in breast as compared to abdominal skin or in barrier-disrupted as compared to intact skin, confirming that the stratum corneum is the main barrier for tacrolimus skin penetration. The anti-proliferative effect of the penetrated drug was measured in skin tissue/Jurkat cells co-cultures. Interestingly, tNGs exhibited similar anti-proliferative effects as the 0.1% tacrolimus ointment. We conclude that polyglycerol-based nanogels represent an interesting alternative to paraffin-based formulations for the treatment of inflammatory skin conditions.

Heterogeneity of Human Mast Cells With Respect to MRGPRX2 Receptor Expression and Function

Mast cells and their mediators play a role in the control of homeostasis and in the pathogenesis of several disorders. The concept of rodent mast cell heterogeneity, initially established in the mid-1960s has been extended in humans. Human mast cells isolated and purified from different anatomic sites can be activated via aggregation of cell surface high affinity IgE receptors (FcεRI) by antigens, superantigens, anti-IgE, and anti-FcεRI. MAS-related G protein-coupled receptor-X2 (MRGPRX2) is expressed at high level in human skin mast cells (MCs) (HSMCs), synovial MCs (HSyMCs), but not in lung MCs (HLMCs). MRGPX2 can be activated by neuropeptide substance P, several opioids, cationic drugs, and 48/80. Substance P (5 × 10⁻⁷ M – 5 × 10⁻⁶ M) induced histamine and tryptase release from HSMCs and to a lesser extent from HSyMCs, but not from HLMCs and human cardiac MCs (HHMCs). Morphine (10⁻⁵ M – 3 × 10⁻⁴ M) selectively induced histamine and tryptase release from HSMCs, but not from HLMCs and HHMCs. SP and morphine were incomplete secretagogues because they did not induce the de novo synthesis of arachidonic acid metabolites from human mast cells. In the same experiments anti-IgE (3 μg/ml) induced the release of histamine and tryptase and the de novo synthesis of prostaglandin D₂ (PGD₂) from HLMCs, HHMCs, HSyMCs, and HSMCs. By contrast, anti-IgE induced the production of leukotriene C₄ (LTC₄) from HLMCs, HHMCs, HSyMCs, but not from HSMCs. These results are compatible with the heterogeneous expression and function of MRGPRX2 receptor on primary human mast cells isolated from different anatomic sites.

Interventions for hand eczema

BACKGROUND

Hand eczema is an inflammation of the skin of the hands that tends to run a chronic, relapsing course. This common condition is often associated with itch, social stigma, and impairment in employment. Many different interventions of unknown effectiveness are used to treat hand eczema.

OBJECTIVES

To assess the effects of topical and systemic interventions for hand eczema in adults and children.

SEARCH METHODS

We searched the following up to April 2018: Cochrane Skin Group Specialised Register, CENTRAL, MEDLINE, Embase, AMED, LILACS, GREAT, and four trials registries. We checked the reference lists of included studies for further references to relevant trials.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared interventions for hand eczema, regardless of hand eczema type and other affected sites, versus no treatment, placebo, vehicle, or active treatments.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Primary outcomes were participant- and investigator-rated good/excellent control of symptoms, and adverse events.

MAIN RESULTS

We included 60 RCTs, conducted in secondary care (5469 participants with mild to severe chronic hand eczema). Most participants were over 18 years old. The duration of treatment was short, generally up to four months. Only 24 studies included a follow-up period. Clinical heterogeneity in treatments and outcome measures was evident. Few studies performed head-to-head comparisons of different interventions. Risk of bias varied considerably, with only five studies at low risk in all domains. Twenty-two studies were industry-funded.Eighteen trials studied topical corticosteroids or calcineurin inhibitors; 10 studies, phototherapy; three studies, systemic immunosuppressives; and five studies, oral retinoids. Most studies compared an active intervention against no treatment, variants of the same medication, or placebo (or vehicle). Below, we present results from the main comparisons.Corticosteroid creams/ointments: when assessed 15 days after the start of treatment, clobetasol propionate 0.05% foam probably improves participant-rated control of symptoms compared to vehicle (risk ratio (RR) 2.32, 95% confidence interval (CI) 1.38 to 3.91; number needed to treat for an additional beneficial outcome (NNTB) 3, 95% CI 2 to 8; 1 study, 125 participants); the effect of clobetasol compared to vehicle for investigator-rated improvement is less clear (RR 1.43, 95% CI 0.86 to 2.40). More participants had at least one adverse event with clobetasol (11/62 versus 5/63; RR 2.24, 95% CI 0.82 to 6.06), including application site burning/pruritus. This evidence was rated as moderate certainty.When assessed 36 weeks after the start of treatment, mometasone furoate cream used thrice weekly may slightly improve investigator-rated symptom control compared to twice weekly (RR 1.23, 95% CI 0.94 to 1.61; 1 study, 72 participants) after remission is reached. Participant-rated symptoms were not measured. Some mild atrophy was reported in both groups (RR 1.76, 95% CI 0.45 to 6.83; 5/35 versus 3/37). This evidence was rated as low certainty.Irradiation with ultraviolet (UV) light: local combination ultraviolet light therapy (PUVA) may lead to improvement in investigator-rated symptom control when compared to local narrow-band UVB after 12 weeks of treatment (RR 0.50, 95% CI 0.22 to 1.16; 1 study, 60 participants). However, the 95% CI indicates that PUVA might make little or no difference. Participant-rated symptoms were not measured. Adverse events (mainly erythema) were reported by 9/30 participants in the narrow-band UVB group versus none in the PUVA group. This evidence was rated as moderate certainty.Topical calcineurin inhibitors: tacrolimus 0.1% over two weeks probably improves investigator-rated symptom control measured after three weeks compared to vehicle (14/14 tacrolimus versus 0/14 vehicle; 1 study). Participant-rated symptoms were not measured. Four of 14 people in the tacrolimus group versus zero in the vehicle group had well-tolerated application site burning/itching.A within-participant study in 16 participants compared 0.1% tacrolimus to 0.1% mometasone furoate but did not measure investigator- or participant-rated symptoms. Both treatments were well tolerated when assessed at two weeks during four weeks of treatment.Evidence from these studies was rated as moderate certainty.Oral interventions: oral cyclosporin 3 mg/kg/d probably slightly improves investigator-rated (RR 1.88, 95% CI 0.88 to 3.99; 1 study, 34 participants) or participant-rated (RR 1.25, 95% CI 0.69 to 2.27) control of symptoms compared to topical betamethasone dipropionate 0.05% after six weeks of treatment. The risk of adverse events such as dizziness was similar between groups (up to 36 weeks; RR 1.22, 95% CI 0.80 to 1.86, n = 55; 15/27 betamethasone versus 19/28 cyclosporin). The evidence was rated as moderate certainty.Alitretinoin 10 mg improves investigator-rated symptom control compared with placebo (RR 1.58, 95% CI 1.20 to 2.07; NNTB 11, 95% CI 6.3 to 26.5; 2 studies, n = 781) and alitretinoin 30 mg also improves this outcome compared with placebo (RR 2.75, 95% CI 2.20 to 3.43; NNTB 4, 95% CI 3 to 5; 2 studies, n = 1210). Similar results were found for participant-rated symptom control: alitretinoin 10 mg RR 1.73 (95% CI 1.25 to 2.40) and 30 mg RR 2.75 (95% CI 2.18 to 3.48). Evidence was rated as high certainty. The number of adverse events (including headache) probably did not differ between alitretinoin 10 mg and placebo (RR 1.01, 95% CI 0.66 to 1.55; 1 study, n = 158; moderate-certainty evidence), but the risk of headache increased with alitretinoin 30 mg (RR 3.43, 95% CI 2.45 to 4.81; 2 studies, n = 1210; high-certainty evidence). Outcomes were assessed between 48 and 72 weeks.

AUTHORS' CONCLUSIONS

Most findings were from single studies with low precision, so they should be interpreted with caution. Topical corticosteroids and UV phototherapy were two of the major standard treatments, but evidence is insufficient to support one specific treatment over another. The effect of topical calcineurin inhibitors is not certain. Alitretinoin is more effective than placebo in controlling symptoms, but advantages over other treatments need evaluating.Well-designed and well-reported, long-term (more than three months), head-to-head studies comparing different treatments are needed. Consensus is required regarding the definition of hand eczema and its subtypes, and a standard severity scale should be established.The main limitation was heterogeneity between studies. Small sample size impacted our ability to detect differences between treatments.

Immunomodulatory effects of tacrolimus (FK506) for the treatment of allergic diseases

Tacrolimus has been used to prevent allograft rejection and also used in kidney, liver and heart transplantations. Various preclinical and clinical studies demonstrated that Tacrolimus possess immunomodulatory and anti-inflammatory properties. The mechanism of action of Tacrolimus in allergic diseases involves calcineurin inhibition, and downregulation of T-cell reactivity, IgE degranulation, and its actions on mast cells, dendritic cells, basophils, eosinophils and inhibition of transcription of proinflammatory cytokines. Herein we reviewed the Pharmacotherapeutic mechanism of action of Tacrolimus in the prevention of asthma, atopic dermatitis, and allergic conjunctivitis.

Tacrolimus ointment for the treatment of adult and pediatric atopic dermatitis: Review on safety and benefits

Atopic dermatitis (AD) requires long-term management, mainly with topical anti-inflammatory agents. Topical corticosteroids (TCS) and tacrolimus ointment (TAC-O) are recommended as first-line treatments for AD. However, the long-term use of TCS is limited by cutaneous adverse events such as skin atrophy. For TAC-O, Japanese and US labelings were updated in 2003 and 2006, respectively, to include a boxed warning about a theoretical risk of skin cancer and lymphoma in patients treated with topical calcineurin inhibitors. However, TAC-O has been used worldwide for longer than 15 years to treat adult and pediatric patients with AD. Available data suggest that TAC-O is effective and well tolerated, and can improve quality of life. TAC-O has successfully been used in the proactive management of AD consisting of long-term intermittent use to prevent, delay or reduce the occurrence of AD flares. Systemic drug absorption after TAC-O application is negligible and unlikely to result in systemic immunosuppression. There is currently no strong evidence of an increased rate of malignancy in treated patients, and observational data from postmarketing surveillance studies have shown no safety concerns. In the absence of robust evidence, the warning about the carcinogenic potential in the Japanese labeling for TAC-O does not appear justified and should be reconsidered. This mitigation of description would allow adult and pediatric patients with AD to receive the effective treatment more appropriately.

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.

Tacrolimus nanoparticles based on chitosan combined with nicotinamide: enhancing percutaneous delivery and treatment efficacy for atopic dermatitis and reducing dose

Background

Topical application of tacrolimus (FK506) was effective in the treatment of atopic dermatitis (AD); however, adverse effects frequently occurred with the increase of FK506 dose during long–term treatment.

Objective

The objective of this project was to develop a hybrid skin targeting system encapsulating FK506 based on nicotinamide (NIC) and chitosan nanoparticles (CS–NPs), ie, FK506–NIC–CS–NPs, which took advantages of both of NIC and CS–NPs to obtain the synergetic effects of percutaneous delivery and treatment efficacy enhancement along with dose reduction.

Methods

The formulation of FK506–NIC–CS–NPs was optimized and characterized. In vitro and in vivo skin permeation studies were performed. AD–like skin lesions were constructed with BALB/c mice by 1–chloro–2, 4–dinitrobenzene (DNCB)–induced, and FK506–NIC–CS–NPs containing different dose of FK506 were topically administered to treat AD–like skin lesions in comparison with Protopic.

Results

NIC was found to significantly increase the FK506 EE to 92.2% by CS–NPs. In comparison with commercial FK506 ointment (Protopic), in vitro and in vivo skin permeation studies demonstrated that NIC–CS–NPs system significantly enhanced FK506 permeation through and into the skin, and deposited more FK506 into the skin. The treatment efficacy on clinical symptoms, histological analysis, and molecular biology of the AD–mice demonstrated that NIC–CS–NPs with ~1/3 dose of FK506 of Protopic was superior to that of Protopic, and NIC–CS–NPs vehicle exhibited the adjuvant therapy and moderate anti–AD effects.

Conclusion

The system of NIC–CS–NPs enhances the permeability of FK506, plays an adjuvant role in anti-AD, reduces the dose of FK506 in treating AD, and is therefore a promising nanoscale system of FK506 for the effective treatment of AD.

Tacrolimus in Dermatology

Background:

Tacrolimus (FK 506), a metabolite of the fungus Streptomyces tsukubaensis, is an anti-T-cell drug. It acts by inhibiting the production of IL-2, IL-3, IL-4, TNFα, and GM-CSF. More potent and with slightly less secondary effects than cyclosporine, it has been the object of considerable interest, especially in conditions that could benefit from the latter.

Objective:

In psoriasis, a placebo-controlled double-blind study has shown oral tacrolimus at 0.1 mg/kg/day to be effective in controlling recalcitrant lesions. In human, small studies have reported tacrolimus ointment to be effective in controlling acute contact dermatitis. Short-term trials of topical tacrolimus in the treatment of atopic dermatitis have recently shown excellent results in both adults and children. In animal studies of hair growth disorders, topical tacrolimus induces anagen and protects from chemotherapy-induced alopecia. Animal studies with the ointment for the prevention of skin graft rejection, lupus dermatoses, and skin papilloma formation have also shown to be promising.

Conclusions:

There are case reports of pyoderma gangrenosum, Sezary's syndrome, and Behçet's disease successfully treated with oral tacrolimus but, because of their small number, they remain anecdotal at this point.

Efficacy and safety of low-dose topical tacrolimus in vernal keratoconjunctivitis

Objective

The objective of this study was to evaluate the efficacy and safety of topical low-dose tacrolimus (0.01%) solution in patients with vernal keratoconjunctivitis (VKC).

Patients and methods

A total of 62 consecutive patients with VKC refractory to conventional treatment were included retrospectively. Tacrolimus 0.01% ophthalmic solution was administered to patients twice daily after discontinuation of all previous topical medications. The duration of treatment ranged from 1 month to 29 months. The clinical symptoms of itching, redness, foreign body sensation, and discharge and the clinical signs of conjunctival hyperemia, conjunctival papillary hypertrophy, limbal infiltration, Trantas dots, and superficial punctate keratopathy were graded as 0 (normal), 1+ (mild), 2+ (moderate), or 3+ (severe). Assessment was carried out before initiation of therapy and on the last visit after treatment.

Results

There were 62 patients with VKC comprising 49 male and 13 female patients. The median age was 12 years (range: 5–47 years). The mean visual acuity improved from 20/30 to 20/25 following treatment. There was statistically significant improvement in symptoms of itching (P<0.001), redness (P<0.001), foreign body sensation (P<0.001), and discharge (P<0.001). Statistically significant improvement was also observed in clinical signs of conjunctival hyperemia (P<0.001), limbal infiltration (P<0.001), Trantas dots (P<0.001), superficial punctate keratopathy (P<0.001), and conjunctival papillary hypertrophy (P<0.001). The solution form of tacrolimus was well tolerated. None of the patients developed elevation of intraocular pressure, cataract, or infectious keratitis.

Conclusion

Low-dose topical tacrolimus 0.01% solution is effective and safe in the management of patients with refractory VKC.

Immunopharmacological modulation of mast cells

Mast cells produce a wide spectrum of mediators and they have been implicated in several physiopathological conditions (e.g. allergic reactions and certain tumors). Pharmacologic agents that modulate the release of mediators from mast cells has helped to elucidate the biochemical mechanisms by which immunological and non-immunological stimuli activate these cells. Furthermore, the study of surface receptors and signaling pathways associated with mast cell activation revealed novel pharmacologic targets. Thus, the development of pharmacologic agents based on this new wave of knowledge holds promise for the treatment of several mast cell-mediated disorders.

Mast cell mediator responses and their suppression by pathogenic and commensal microorganisms

Mast cells (MCs) are selectively found at the host environment interface and are capable of secreting a wide array of pharmacologically active mediators, many of which are prepackaged in granules. Over the past two decades, it has become clear that these cells have the capacity to recognize a range of infectious agents allowing them to play a key role in initiating and modulating early immune responses to infectious agents. However, a number of pathogenic and commensal microbes appear to have evolved distinct mechanisms to suppress MC mediator release to avoid elimination in the host. Understanding how these microbes suppress MC functions may have significant therapeutic value to relieve inflammatory disorders mediated by MCs.

Calcineurin inhibitors in chronic urticaria

PURPOSE OF REVIEW

The purpose of the review is to review the pathophysiology, available data, and our current recommendations for calcineurin inhibitor (cyclosporine and tacrolimus) treatment in antihistamine refractory chronic idiopathic urticaria (CIU) patients.

RECENT FINDINGS

Low-dose cyclosporine (<5  mg/kg per day) may have unique immunological modulating properties beyond mast cell and basophil stabilization in CIU. Starting CIU treatment with very low cyclosporine dosages (1 mg/kg per day) and titrating based on response and side-effects may decrease adverse events while preserving efficacy. In cyclosporine responsive patients failing cyclosporine taper, case series data support the safety and efficacy of long-term (5-10 years), very low dose (1-2 mg/kg per day) cyclosporine treatment with appropriate clinical monitoring.

SUMMARY

For CIU patients refractory to antihistamines, low-dose cyclosporine therapy (<3 mg/kg per day) with appropriate laboratory monitoring provides an alternative with an acceptable side-effect profile. Long-term (>12 months) moderate-dose (2.5-5 mg/kg per day) cyclosporine treatment may cause longitudinal increases in serum creatinine. However, decreasing or stopping cyclosporine dosing reverses measured nephrotoxicity in the vast majority of patients, and some patients with careful monitoring can tolerate very low-dose cyclosporine (<2 mg/kg per day) for longer periods. Tacrolimus is an alternative to cyclosporine with a slightly different adverse effect profile. Minimal data are available on its use in chronic urticaria.

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.

Updates in the treatment of ocular allergies

Allergic diseases have greatly increased in industrialized countries. About 30% of people suffer from allergic symptoms and 40%–80% of them have symptoms in the eyes. Atopic conjunctivitis can be divided into seasonal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC). The treatment of SAC is simple; antihistamines, anti-inflammatory agents, or chromoglycate. In severe cases of SAC, subcutaneous or sublingual immunotherapy is helpful. PAC needs longer therapy, often year round, with mast cell stabilizers, antihistamines, and sometimes local steroids. Atopic keratoconjunctivitis is a more severe disease showing chronic blepharitis often connected with severe keratitis. It needs, in many cases, continuous treatment of the lid eczema and keratoconjunctivitis. Blepharitis is treated with tacrolimus or pimecrolimus ointment. Conjunctivitis additionally needs corticosteroids and, if needed, cyclosporine A (CsA) drops are administered for longer periods. Basic conjunctival treatment is with mast cell-stabilizing agents and in addition, antihistamines are administered. Vernal keratoconjunctivitis is another chronic and serious allergic disease that mainly affects children and young people. It is a long-lasting disease which commonly subsides in puberty. It demands intensive therapy often for many years to avoid serious complicating corneal ulcers. Treatment is mast cell-stabilizing drops and additionally antihistamines. In relapses, corticosteroids are needed. When the use of corticosteroids is continuous, CsA drops should be used, and in relapses, corticosteroids should be used additionally. Nonallergic eosinophilic conjunctivitis (NAEC) is a less known, but rather common, ocular disease. It affects mostly middle-aged and older women. The eye symptoms of NAEC are largely similar to those seen in chronic allergic conjunctivitis. Basic therapy is mast cell-stabilizing drops. Eosinophilic inflammation needs additional corticosteroids. In severe cases, CsA drops are recommended. Antihistamines should be avoided. It is important to recognize the different forms of allergic ocular diseases and to start the treatment early and intensively enough to avoid chronicity of the disease and accompanying tissue destruction.

Participation of proteinase-activated receptor-2 in passive cutaneous anaphylaxis-induced scratching behavior and the inhibitory effect of tacrolimus

Proteinase-activated receptor-2 (PAR2) may be an important regulator of skin mast cell function during cutaneous inflammation and hypersensitivity. However, little is known of the role of PAR2 in allergic pruritus, because mast cells, which are thought to be responsible for this symptom, can release a number of different pruritogens. In the present study, we investigated the effects of several agents on passive cutaneous anaphylaxis-induced scratching behavior in ICR mice. As a result, cetirizine and ketanserin produced dose-dependent inhibition of scratching behavior induced by passive cutaneous anaphylaxis. Combined cetirizine with ketanserin exhibited significant inhibitory effects for the number of passive cutaneous anaphylaxis-induced scratching behavior. Pretreatment of the experimental animals with PAR2-neutralizing antibody and protease inhibitor leupeptin significantly inhibited passive cutaneous anaphylaxis-induced scratching behavior. Furthermore, we found that topical application of tacrolimus significantly reduced the number of scratching behavior induced by passive cutaneous anaphylaxis in a dose-dependent manner. Combined cetirizine with tacrolimus also exhibited significant inhibitory effects for the number of passive cutaneous anaphylaxis-induced scratching behavior. Tacrolimus in doses of 3% and 10% significantly inhibited tryptase-induced scratching behavior. These results suggest that PAR2 may be involved in passive cutaneous anaphylaxis-induced scratching behavior and tacrolimus produces an anti-allergic pruritus effect in ICR mice.

Dexamethasone and FK506 inhibit expression of distinct subsets of chemokines in human mast cells

Mast cells produce a large amount of several chemokines after cross-linking of FcepsilonRI and participate in the pathogenesis of allergic diseases. The objective of this study was to comprehensively investigate FcepsilonRI-mediated chemokine induction in human mast cells and the effect of a corticosteroid (dexamethasone) and a calcineurin inhibitor (FK506). Human peripheral blood-derived mast cells were stimulated with anti-IgE Ab in the presence of dexamethasone or FK506. Gene expression profiles were evaluated using GeneChip and confirmed by real-time PCR, and chemokine concentrations were measured by cytometric bead arrays and ELISA. Expression of eight chemokines was significantly induced in mast cells by anti-IgE stimulation. Induction of CCL2, CCL7, CXCL3, and CXCL8 by anti-IgE was significantly inhibited by dexamethasone but was enhanced by FK506. In contrast, induction of CCL1, CCL3, CCL4, and CCL18 was significantly inhibited by FK506 but, with the exception of CCL1, was enhanced by dexamethasone. Combination of dexamethasone and FK506 suppressed production of all chemokines by anti-IgE stimulation. Studies using protease inhibitors indicate that mast cell proteases may degrade several of the chemokines. These results suggest that corticosteroids and calcineurin inhibitors inhibit expression of distinct subsets of chemokines, and a combination of these drugs almost completely suppresses the induction of all chemokine genes in human mast cells in response to FcepsilonRI-dependent stimulation. This implies that a combination of a corticosteroid and a calcineurin inhibitor may be more effective than each single agent for the treatment of allergic diseases in which mast cell-derived chemokines play a major role.

Effects of topical application of tacrolimus on acute itch-associated responses in mice

Using mice, we examined whether the topical application of tacrolimus would produce an acute anti-pruritic effect. An itch-related response, scratching, was elicited by intradermal injections of mosquito allergen (10 microg/site) in sensitized mice and SLIGRL-NH2 (protease-activated receptor-2 agonist, 50 nmol/site), histamine (100 nmol/site), serotonin (100 nmol/site) and substance P (100 nmol/site) in naive ones. Topical application of 1%, but neither 0.1% nor 0.3%, tacrolimus to the skin 1 h before injection inhibited scratching induced by mosquito allergen and SLIGRL-NH2, without effects on scratching induced by histamine, serotonin, and substance P. Topical tacrolimus also inhibited licking induced by an intraplantar injection of capsaicin (0.1 microg/site). These results suggest that topical tacrolimus exerts acute inhibitory effects on allergic and protease-activated receptor-2-mediated itching. Though precise mechanisms remain unclear, the action on sensory neurons expressing protease-activated receptor-2 and transient receptor potential vanilloid-1 capsaicin receptor may be involved in the inhibitory effects of tacrolimus.

Tacrolimus in dermatology-pharmacokinetics, mechanism of action, drug interactions, dosages, and side effects: part I

The advent of tacrolimus at the end of the preceding century in the armamentarium of atopic dermatitis management was hailed as a breakthrough advance. It was, therefore, thought worthwhile to precisely review its origin and mechanism of action. Its topical application in the form of 0.03% to 0.1% ointments is rapidly effective and safe in pediatric and adult patients. Its use in atopic dermatitis ever since has been approved in Japan, the United States, Europe, and the Indian subcontinent. Thus, its local immunosuppressive action was fairly intriguing. Accordingly, its indications/uses were extended to cover several inflammatory dermatoses. Vitiligo, psoriasis, alopecia areata, contact hypersensitivity, lichen planus, pyoderma gangrenosum, ichthyosis linearis circumflexa, and skin grafting/transplant are a few unapproved indications and uses, in addition to miscellaneous dermatoses. At present, its therapeutic efficacy other then atopic dermatitis is confined to case studies, and large studies are warranted. At this point in time, therefore, it is conceivable that tacrolimus use should be carefully evaluated and used only when the conventional treatment has failed to yield favorable results. It deserves sizable caution for use in various dermatologic conditions pending its long-term safety and efficacy data in large patient populations.

Immunology and treatment of atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory disease hypothesized to be the product of complex interactions among the host's environment, susceptibility genes, skin barrier dysfunction, and immune system dysregulation. The objective of this article is to describe the pathobiology and treatment of AD, with particular focus on the role of immune system dysregulation and therapies designed to target this. Literature review indicates that there are immunologic differences between the lesional and non-lesional skin of atopic individuals, and that the non-lesional skin of atopic individuals presents an immunologic profile distinct from that of the skin of healthy individuals. Thus, immune system dysregulation is postulated to be a key contributing factor to the complex etiology of AD. Immunomodulatory agents such as topical corticosteroids (TCSs) and topical calcineurin inhibitors (TCIs), which address the underlying immunopathology of AD, are the foundation for the pharmacologic treatment of flares. TCSs and TCIs both target the inflammatory response responsible for an AD flare but via two distinct mechanisms of action. Whereas TCSs have a more widespread impact on the immune system, the action of TCIs is targeted to the calcineurin pathway and inhibition of T-cell activation. Together, TCSs and TCIs represent the backbone of a long-term treatment strategy for AD.

Topical 0.1% tacrolimus for the treatment of discoid lupus erythematosus and pemphigus erythematosus in dogs

Topical 0.1% tacrolimus was used for treatment of localized lesions associated with 10 cases of discoid lupus erythematosus (DLE) and two cases of pemphigus erythematosus (PE) either as a sole therapy (n=2) or as an adjunctive treatment (n=10). Eight of 10 dogs with DLE and both dogs with PE were improved following 8 weeks of topical application. In six of the eight dogs that improved, other medications were discontinued. No adverse effects in clinical or laboratory parameters were noted throughout the study.

Topical pimecrolimus and tacrolimus transiently induce neuropeptide release and mast cell degranulation in murine skin

BACKGROUND

The topical calcineurin inhibitors pimecrolimus and tacrolimus have been demonstrated to be an effective new anti-inflammatory therapy. The only clinically relevant side-effect reported is transient application site burning and stinging itch at the beginning of topical therapy.

OBJECTIVES

In order to understand the underlying mechanism of this effect, we examined whether or not the compounds are able to stimulate neuropeptide release in normal murine skin as well as in a mouse model of experimentally induced irritant contact dermatitis.

METHODS

Balb/c mice were treated with 1% pimecrolimus cream or 0.1% tacrolimus ointment. Untreated and corresponding vehicle-treated mice served as controls. Skin specimens were investigated by light, immunofluorescence and electron microscopy as well as enzyme-linked immunosorbent assay and polymerase chain reaction.

RESULTS

Topical application of pimecrolimus and tacrolimus was followed by an initial release of substance P and calcitonin gene-related peptide from primary afferent nerve fibres in murine skin during the early inflammatory response. The release of the neuropeptides and their binding to mast cells (MCs) led to MC degranulation. Mediators of MCs such as histamine and tryptase may induce pruritus and burning by binding to the corresponding receptors (histamine receptor 1, proteinase-activated receptor 2) on sensory nerve fibres, which explains the initial side-effects during therapy with calcineurin inhibitors.

CONCLUSIONS

It may be speculated that calcineurin inhibitors directly stimulate intracellular signalling pathways or bind to ion channels such as transient receptor potential vanilloid 1 or receptors involved in nociception.

Comparison of the efficacy and safety of 0.1% tacrolimus ointment with topical corticosteroids in adult patients with atopic dermatitis: review of randomised, double-blind clinical studies conducted in Japan

Tacrolimus (FK506) ointment is widely used in the treatment of patients with atopic dermatitis. The drug exerts its action by down-regulating antigen-specific T-cell activities and associated proinflammatory cytokine production. A number of clinical studies have evaluated the efficacy and safety of 0.1% tacrolimus ointment compared with vehicle or topical corticosteroids in adult patients with atopic dermatitis. These studies have suggested that topical tacrolimus has a rapid onset of action and exerts sustained therapeutic effects, with an efficacy similar to that of moderate to potent topical corticosteroids, but without causing skin atrophy. Two phase III randomised, controlled clinical trials have been conducted in Japanese adult patients with atopic dermatitis to compare the efficacy and safety of topical 0.1% tacrolimus with topical corticosteroid ointments. In the first study, patients with moderate or severe atopic dermatitis on the trunk and extremities were randomised to 3 weeks of treatment with topical 0.1% tacrolimus or the mid-potency topical corticosteroid 0.12% betamethasone valerate. Over 90% of the patients in each study group experienced at least a moderate improvement at the end of the study. In the second study, patients with moderate or severe atopic dermatitis on the head or neck were randomised to 1 week of treatment with 0.1% tacrolimus or the mild-potency corticosteroid 0.1% alclometasone dipropionate. Significantly greater improvements in individual symptom scores were observed with topical tacrolimus compared with alclometasone dipropionate, with overall global improvement at 1 week being statistically superior with tacrolimus. Furthermore, in a long-term open-label study involving 568 patients, at least a moderate global improvement in symptoms was observed in 85% of patients at 6 weeks, increasing to 91% at both 26 weeks and 52 weeks; this rate was maintained throughout the 2-year duration of the study. 0.1% tacrolimus ointment was considered to be safe in the majority of patients. The most prevalent adverse reactions were local application site irritations, which generally resolved with continued therapy. In summary, these findings suggest that 0.1% tacrolimus ointment is an effective and safe nonsteroidal alternative therapy for adult patients with atopic dermatitis.

Role of calcineurin in the regulation of human lung mast cell and basophil function by cyclosporine and FK506

BACKGROUND AND PURPOSE

Cyclosporine and FK506 are thought to act by targeting the Ca2+-dependent protein phosphatase, calcineurin. The aim of the present study was to determine whether cyclosporine and FK506 stabilize mast cells and basophils by interacting with calcineurin.

EXPERIMENTAL APPROACH

The effects of cyclosporine and FK506 on the IgE-mediated release of histamine from mast cells and basophils were evaluated. The presence of calcineurin in cells was determined by Western blotting. Ca2+-dependent protein phosphatase activities were assessed in cell extracts using a synthetic phosphorylated peptide that is known to serve as a substrate for calcineurin.

KEY RESULTS

FK506 was about 100-fold more potent than cyclosporine as an inhibitor of IgE-dependent histamine release from mast cells and basophils. Immunoblotting of solubilized preparations of purified cells demonstrated the presence of calcineurin in mast cells and basophils. In enzyme assays, mast cells expressed approximately 7-fold higher Ca2+-dependent protein phosphatase activity than basophils. Whereas cyclosporine effectively inhibited Ca2+-dependent protein phosphatase activity in cell extracts, FK506 was considerably less effective.

CONCLUSIONS AND IMPLICATIONS

FK506 and cyclosporine inhibit the stimulated release of histamine from mast cells and basophils. However, the ability of cyclosporine, but not FK506, to inhibit Ca2+-dependent protein phosphatase activity questions whether FK506 stabilizes mast cells and basophils by interacting with calcineurin.

Wirksamkeit von Tacrolimus-0,1-%-Salbe bei Prurigoerkrankungen. Efficacy of tacrolimus 0.1 % ointment in prurigo

BACKGROUND

Potent topical corticosteroids are used the intense pruritus in prurigo diseases. Their long-term application leads to local side effects such as atrophy and telangiectasia.

PATIENTS AND METHODS

We treated 6 women (average age 64 years) with chronic prurigo with tacrolimus 0.1 % ointment (Protopic) to evaluate its efficacy in this clinical setting. Tacrolimus 0.1% ointment was applied twice a day for 4 weeks.

RESULTS

After one week, both clinical improvement and reduced pruritus were observed in all patients.

CONCLUSION

Tacrolimus 0.1% ointment represents a therapeutic option for the treatment of prurigo.

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.

Mechanisms of action of topical therapies and the rationale for combination therapy

The advent of new topical agents such as topical calcineurin inhibitors, as well as the reformulations of older agents in new vehicles, has broadened the treatment approaches to psoriasis and atopic dermatitis. The clinician must now consider additional novel physiologic pathways and mechanisms of action as well as expanding options for combination therapy. Combination therapy is especially beneficial when the selected agents possess differing mechanisms of action that provide additive or synergistic efficacy, reducing the required doses of the individual agents compared with monotherapy and potentially limiting side effects. Therapeutic approaches also can be rotated or used in various sequences for maintenance therapy. In psoriasis, a number of trials have demonstrated the effectiveness of combination therapy. Although combination therapy has not been extensively studied in atopic dermatitis, many practitioners combine topical corticosteroids and topical calcineurin inhibitors in their clinical practice because the two drug classes have different and possibly complementary mechanisms of action. For both diseases, the decision as to what agents are combined must also be tempered by patient type, disease presentation or severity, and patient preferences.

Calcineurin Inhibitors: A Novel Approach to Canine Atopic Dermatitis

The introduction of calcineurin inhibitors represents a major addition to the armamentarium of drugs available to veterinary clinicians for the management of allergic skin diseases. Both cyclosporine and tacrolimus have been proven to be well tolerated and effective for the treatment of atopic dermatitis in dogs. Although broad spectrum in their mechanism of action, they lack the major adverse effects of glucocorticoids and provide an appealing alternative to traditional therapies. The purposes of this article are to review clinically relevant information regarding these agents and to provide tips for maximizing the benefit obtained from these therapies.

New Treatment Modalities for Vitiligo

The development of effective treatment modalities for vitiligo is dependent on an understanding of the events leading to depigmentation. However, the exact pathogenesis of vitiligo is still mostly unknown. Abnormalities in both humoral and cell-mediated immunity have been documented in vitiligo patients and they present a basis for using immunomodulating agents, such as corticosteroids and macrolide immunomodulators, in the treatment of vitiligo. Macrolide immunomodulators, such as tacrolimus and pimecrolimus, which can be used topically, are known as topical immunomodulators (TIMs). TIMs inhibit the action of calcineurin, and consequently inhibit T-cell activation and the production of various cytokines; this is considered the working mechanism of action of TIMs in vitiligo. Several small studies and case reports on the use of TIMs in vitiligo have been published so far. Tacrolimus achieves better results on the face and neck than on other body areas. Particular advantages of TIMs are safety in treating these areas because of lack of skin atrophy and good tolerability. The incidence of application site adverse events in vitiligo seems to be lower than in the treatment of atopic dermatitis. On the face and neck, TIMs may become a useful tool in the treatment of adults and children with vitiligo despite possibly lower efficacy than topical corticosteroids. Further, larger, controlled clinical studies are warranted to determine the definite role of TIMs as monotherapy or in combination with other modalities in the treatment of vitiligo.

Role of human mast cells and basophils in bronchial asthma

Mast cells and basophils are the only cells expressing the tetrameric (alphabetagamma2) structure of the high affinity receptor for IgE (FcepsilonRI) and synthesizing histamine in humans. Human FcepsilonRI+ cells are conventionally considered primary effector cells of bronchial asthma. There is now compelling evidence that these cells differ immunologically, biochemically, and pharmacologically, which suggests that they might play distinct roles in the appearance and fluctuation of the asthma phenotype. Recent data have revealed the complexity of the involvement of human mast cells and basophils in asthma and have shed light on the control of recruitment and activation of these cells in different lung compartments. Preliminary evidence suggests that these cells might not always be detrimental in asthma but, under some circumstances, they might exert a protective effect by modulating certain aspects of innate and acquired immunity and allergic inflammation.

Tacrolimus Ointment

Tacrolimus ointment (Protopic) is a topically applied macrolide lactone immunomodulator effective in the treatment of atopic dermatitis. Its mechanism of action primarily involves calcineurin inhibition, which interrupts cytokine gene expression and leads to the downregulation of T-cell activity. Tacrolimus ointment (0.03% and 0.1% for adults and 0.03% for children) is an effective treatment for atopic dermatitis of the trunk and limbs, as well as sensitive skin areas such as the face. Its efficacy is similar to or greater than that of hydrocortisone acetate 1%, hydrocortisone butyrate 0.1% and betamethsone valerate 0.12% ointments and pimecrolimus 1% cream. Systemic absorption of tacrolimus from the ointment is minimal, and adverse events, which are mostly associated with the application site and include skin burning and pruritus, tend to resolve early in treatment. Unlike topical corticosteroids, tacrolimus ointment is not associated with skin atrophy, and it is a well tolerated treatment for adults or children with atopic dermatitis, particularly when long-term treatment is indicated or the face or skin-fold regions are involved.

Investigation on the clinical efficacy and safety of 0.1% tacrolimus ointment (Protopic) in canine atopic dermatitis: a randomized, double-blinded, placebo-controlled, cross-over study

Topical tacrolimus is successfully used in people with atopic dermatitis. Preliminary studies in dogs with atopic dermatitis using tacrolimus in a compounded lotion formulation indicated that tacrolimus significantly decreased erythema and pruritus according to investigator, but no significant improvement was reported by the dog owners. The objectives of this study were to evaluate the clinical efficacy and safety of the commercially available 0.1% tacrolimus ointment (Protopic) in dogs with atopic dermatitis. The study was designed as a double-blinded, placebo-controlled, cross-over study. Selected dogs were allocated to either tacrolimus or placebo for 4 weeks. After 4 weeks there was a wash-out period of 2 weeks and treatments were switched. Twelve dogs completed the study. Clinical signs were scored. Blood samples were collected for complete blood count, chemistry panels and tacrolimus levels at week 0 and 4 of each treatment. Tacrolimus ointment significantly decreased severity of symptoms for both owners and investigators at the end of the trial. When the same dogs received the placebo, there were no differences between week 0 and week 4 scores. Dogs with localized disease responded better than dogs with generalized disease. Tacrolimus was detected in the blood of animals receiving the active ingredient. Levels were below the level of toxicity and no adverse effects were reported in any of the dogs. No changes in complete blood count and chemistry parameters were detected between groups or within groups. In conclusion, tacrolimus appears to be a safe alternative treatment in dogs with atopic dermatitis, especially in those with localized disease.

The role of topical calcineurin inhibitors in atopic dermatitis:

For more than five decades, topical corticosteroids and emollients have been the mainstay of therapy for atopic dermatitis. However, the potential for side-effects limits the clinical utility of corticosteroids in providing long-term disease control. With a unique mode of action that differs from that of corticosteroids, the steroid-free topical calcineurin inhibitors (TCIs), tacrolimus ointment and pimecrolimus cream, provide skin-selective treatment that targets key factors involved in the pathogenesis of this chronic disease. An extensive series of clinical trials involving more than 16,000 patients with predominantly moderate to severe atopic dermatitis in tacrolimus studies and over 2000 patients with primarily mild to moderate disease in pimecrolimus studies has shown that both TCIs provide effective and well-tolerated treatment for atopic dermatitis. Randomized controlled trials have demonstrated that tacrolimus is superior to conventional hydrocortisone-based regimens and does not cause skin atrophy or other steroidal side-effects. Both tacrolimus and pimecrolimus prevent disease flares and provide progressive and sustained disease improvement with long-term therapy. These and other clinical benefits of TCIs are discussed, together with the safety profiles of tacrolimus and pimecrolimus and their use in clinical practice. In addition, this review summarizes findings from the many trials carried out with these agents and outlines how TCIs can provide long-term treatment and control of a chronic skin disease that may persist for years.

Differential effects of FK506 and cyclosporin A on catecholamine release from bovine adrenal chromaffin cells

1 The effects of the immunosuppressants, tacrolimus (FK506) and cyclosporin A (CsA), on catecholamine (CA) release were examined in cultured bovine adrenal chromaffin cells. 2 In intact cells, FK506 (1-30 microM) inhibited CA release stimulated by acetylcholine (ACh; 100 microM), 1,1-dimethyl-4-phenyl-piperazinium (DMPP, 10 microM) or high K+ (40 mM). CsA (1-30 microM) had a little inhibitory effect on the ACh- or DMPP-stimulated CA release, whereas it enhanced the high K(+)-stimulated CA release. 3 In beta-escin-permeabilized cells, FK506 inhibited CA release stimulated by Ca2+ (1 and 10 microM) in the presence and absence of MgATP (2 mM). CsA induced CA release under Ca(2+)-free condition and enhanced the Ca(2+)-stimulated CA release in the presence and absence of MgATP. 4 It is known that the Ca(2+)-dependent exocytosis involves at least two distinct steps, ATP-requiring priming stage and ATP-independent fusion step in adrenal chromaffin cells. Therefore, it is suggested that FK506 inhibits the Ca(2+)-dependent exocytosis probably at the fusion step whereas CsA induces CA release from bovine adrenal chromaffin cells.

Investigation on the effects of topical therapy with 0.1% tacrolimus ointment (ProtopicR) on intradermal skin test reactivity in atopic dogs

Tacrolimus ointment (TAC) is an effective treatment for atopic dermatitis in humans and dogs. The purposes of the present study were to evaluate the effect of 4 weeks of TAC on intradermal skin testing (IST), and in case of suppression, to investigate if reactivity returned to baseline by 2 or 4 weeks post treatment. Intradermal skin test was performed using saline, histamine, lipopolysaccharide (LPS, 0.4 mg mL(-1)), house dust (25 PNU mL(-1)) and house dust mite (1 : 40 000 w/v) at weeks 0, 4, 6 and 8 on nine dogs enrolled in a blinded, crossover, clinical trial, using 0.1% TAC or placebo once daily for 4 weeks. Reactions were evaluated at 15 min, and at 4 and 6 h. Ointment was applied after the 15-min evaluation on weeks 0 and 4. Data were analysed using the statistical software SAS System for Windows. At week 4, TAC did not affect 15-min IST, but some reactions in the TAC group were suppressed at 6 h compared to baseline. In the TAC group, 4-h IST reactivity was reduced 2 weeks after discontinuation but returned to baseline by 4 weeks. In conclusion, TAC has no effect on immediate reactions but decreased some late-phase reactions. Therefore, no withdrawal is recommended to evaluate only immediate reactions, but a 4-week withdrawal may be necessary for evaluation of late-phase reactions.

Effect of FK506 eye drops on late and delayed-type responses in ocular allergy models

BACKGROUND

It is well-known that FK506 strongly inhibits cytokine production by T cells in vitro. However, less evidence is available from in vivo studies of ocular allergy.

OBJECTIVE

To study the anti-inflammatory effect of FK506 eye drops on late and delayed-type responses in several animal models of ocular allergy.

METHODS

Rats and guinea-pigs were sensitized with egg albumin (EA) in adjuvant and later challenged by topical EA application to their eyes to examine the late response. Biopsy specimens of conjunctiva were stained with haematoxylin-eosin or stained for T cells and eosinophils. In addition, rats, rabbits and guinea-pigs were sensitized with complete Freund's adjuvant and later challenged by injecting purified protein derivatives for the delayed-type response. Bulbar conjunctival oedema and hyperaemia were graded by score in rabbits, and Evans blue (EB) extravasation was measured in rats and guinea-pigs. FK506 (0.01-1%) and steroid (0.1%) eye drops were instilled in the eyes of animals several times, before and after challenge.

RESULTS

FK506 eye drops inhibited T cell and eosinophil infiltration in the late response and EB extravasation in the delayed-type response in rats. Also, they inhibited conjunctival oedema, hyperaemia and ocular mucus in the delayed-type response in rabbits. These effects were similar to those of steroid eye drops (betamethasone sodium phosphate, fluorometholone). FK506 eye drops also inhibited inflammatory cell infiltration, the loss of conjunctival epithelium and decrease of goblet cells in the late response as well as EB extravasation in the delayed-type response in guineapigs, a steroid-resistant species.

CONCLUSION

FK506 eye drops inhibit late and delayed-type responses in animal models of ocular allergy.

Effects of immunomodulators on airways hyperresponsiveness to adenosine induced in actively sensitised Brown Norway rats by exposure to allergen

We have recently demonstrated a marked and selective augmentation of the bronchoconstrictor response to adenosine in actively sensitised Brown Norway (BN) rats challenged with ovalbumin (OA). The augmented response is mediated by 5-hydroxytryptamine (5-HT) released as a consequence of mast cell activation. We describe here the effects of budesonide, a clinically used glucocorticosteroid, IMM125, a hydroxyethyl derivative of D-serine-cyclosporine, MLD987, a close analogue of ascomycin and SAR943, a rapamycin derivative, on the hyperresponsiveness to adenosine induced in actively sensitised BN rats by exposure to allergen. Bronchoconstrictor responses to adenosine elicited 3 h following intratracheal (i.t.) instillation of OA, 0.3 mg kg(-1) were reduced dose-dependently by budesonide, IMM125, and MLD987, given i.t. 25 and 1 h prior to allergen challenge. In contrast, SAR943 had no effect on responses to adenosine. Responses to methacholine and 5-HT were minimally affected by these agents. Bronchoconstrictor responses to bradykinin were dose-dependently reduced by budesonide, but unaffected following IMM125, MLD987 or SAR943 pre-treatment. Challenge with OA at a dose of 0.3 mg kg(-1), induced increases in bronchoalveolar lavage (BAL) fluid, leukocyte numbers, eosinophil peroxidase (EPO) and myeloperoxidase (MPO) activities and protein concentration measured 24 h post challenge. Budesonide (1 mg kg(-1) given i.t. 25 and 1 h prior to OA challenge) induced reductions in the BAL fluid parameters of inflammation; IMM125 and MLD987, at a dose of 1 mg kg(-1) had no significant effect whereas SAR943 reduced lymphocyte numbers. Thus, budesonide, IMM125 and MLD987 block the hyperresponsiveness to adenosine induced by allergen challenge in sensitised rats. In the case of budesonide the effect is associated with a powerful, generalised anti-inflammatory effect although an effect directly on the mast cells is also likely. With IMM125 and MLD987, the effect is seen at doses that are not anti-inflammatory and may reflect direct suppression of mast cell activation by these agents.

Tacrolimus ointment for the treatment of vulvar lichen sclerosus

The treatment of vulvar lichen sclerosus is generally considered difficult. Ultrapotent corticosteroids represent the most effective topical treatment, but carry the risk of side effects such as skin atrophy. We describe a 71-year-old woman with long-standing vulvar lichen sclerosus refractory to conventional treatment. After 6 consecutive weeks of treatment with tacrolimus ointment 0.1% (Protopic) twice daily, signs and symptoms of lichen sclerosus resolved. To our knowledge, this is the first report of the use of topical tacrolimus, which does not induce skin atrophy, in the treatment of vulvar lichen sclerosus.

[Antipruritic effects of pimecrolimus and tacrolimus]

The development of topical calcineurin inhibitors resulted in a significant improvement in the treatment of inflammatory skin diseases such as atopic dermatitis. In addition, an excellent amelioration of pruritus could be observed. Other itchy dermatoses such as chronic irritative hand dermatitis, rosacea, graft-versus-host-disease, renal pruritus, lichen sclerosus, prurigo simplex, prurigo nodularis, scrotal eczema, and inverse psoriasis also have been treated successfully with pimecrolimus and tacrolimus. The antipruritic effect currently is believed to be related to the inhibition of inflammatory cytokines. Furthermore, recent investigations indicate a release of neuropeptides from sensory nerve fibers and degranulation of mast cells mediated by pimecrolimus and tacrolimus. Similar effects have been observed during capsaicin treatment. These findings may provide a possible explanation for initially observed calcineurin inhibitors related side-effects such as burning and pruritus. Moreover, the antipruritic potency may be related to a direct effect on nerve fibers leading to suppression of itch mediated by unknown mechanisms.

8-Methoxypsoralen and long-wave ultraviolet A inhibit the release of proinflammatory mediators and cytokines from human Fc epsilon RI+ cells: an in vitro study

The in vitro effects of 8-MOP (concentrations of 20, 100 and 500 ng/ml) alone or in combination with UVA on mediator release from human basophils and skin mast cells (HSMC), activated with immunological and non-immunological stimuli, were investigated. With respect to basophils activated with anti-IgE serum, the results of this study show that: (i) 8-MOP alone inhibits histamine, LTC(4), IL-4 and IL-13 release concentration dependently with a maximal effect at 500 ng/ml (a concentration not reached in vivo); and (ii) UVA irradiation (5 J/cm(2)), after 8-MOP incubation, enhances this inhibitory effect on all released mediators, but for IL-4 and IL-13 the percentage inhibition is also significant for the 8-MOP concentrations (20-100 ng/ml) employed in vivo during PUVA treatment. Moreover, histamine release from basophils activated with non-immunological stimuli (FMLP and A23187) is inhibited by 8-MOP, alone or in combination with UVA. With respect to the HSMC activated with anti-IgE serum, the results show that: (i) 8-MOP alone reduces histamine release concentration dependently; and (ii) this inhibitory effect is enhanced by UVA irradiation (5 J/cm(2)). Histamine release from HSMC activated with A23187 is not modified either by 8-MOP alone or by 8-MOP plus UVA.