FK506 inhibition of histamine release and cytokine production by mast cells and basophils

Suppression of Mast Cell Activation by GPR35: GPR35 Is a Primary Target of Disodium Cromoglycate

Mast cell stabilizers, including disodium cromoglycate (DSCG), were found to have potential as the agonists of an orphan G protein-coupled receptor, GPR35, although it remains to be determined whether GPR35 is expressed in mast cells and involved in suppression of mast cell degranulation. Our purpose in this study is to verify the expression of GPR35 in mast cells and to clarify how GPR35 modulates the degranulation. We explored the roles of GPR35 using an expression system, a mast cell line constitutively expressing rat GPR35, peritoneal mast cells, and bone marrow-derived cultured mast cells. Immediate allergic responses were assessed using the IgE-mediated passive cutaneous anaphylaxis (PCA) model. Various known GPR35 agonists, including DSCG and newly designed compounds, suppressed IgE-mediated degranulation. GPR35 was expressed in mature mast cells but not in immature bone marrow-derived cultured mast cells and the rat mast cell line. Degranulation induced by antigens was significantly downmodulated in the mast cell line stably expressing GPR35. A GPR35 agonist, zaprinast, induced a transient activation of RhoA and a transient decrease in the amount of filamentous actin. GPR35 agonists suppressed the PCA responses in the wild-type mice but not in the GPR35-/- mice. These findings suggest that GPR35 should prevent mast cells from undergoing degranulation induced by IgE-mediated antigen stimulation and be the primary target of mast cell stabilizers. SIGNIFICANCE STATEMENT: The agonists of an orphan G protein-coupled receptor, GPR35, including disodium cromoglycate, were found to suppress degranulation of rat and mouse mature mast cells, and their antiallergic effects were abrogated in the GPR35-/- mice, indicating that the primary target of mast cell stabilizers should be GPR35.

Tacrolimus-Eluting Disk within the Allograft Enables Vascularized Composite Allograft Survival with Site-Specific Immunosuppression without Systemic Toxicity

AIM

Widespread clinical application of vascularized composite allotransplantation (VCA) has been limited by the need for lifelong systemic immunosuppression to prevent rejection. Our goal was to develop a site-specific immunosuppressive strategy that promotes VCA allograft survival and minimizes the risk of systemic side effects.

METHODS

Tacrolimus loaded polycaprolactone (TAC-PCL) disks were prepared and tested for their efficacy in sustaining VCA allograft survival via site-specific immunosuppression. Brown Norway-to-Lewis rat hind limb transplantations were performed; animals received one TAC disk either in the transplanted (DTx) or in the contralateral non-transplanted (DnonTx) limbs. In another group, animals received DTx and lymphadenectomy on Tx side. Blood and allograft levels of TAC were measured using LC-MS/MS. Systemic toxicity was evaluated.

RESULTS

Animals that received DTx achieved long-term allograft survival (> 200 days) without signs of metabolic and infectious complications. In these animals, TAC blood levels were low but stable between 2 to 5 ng/mL for nearly 100 days. High concentrations of TAC were achieved in the allografts and the draining lymph nodes (DLN). Animals that underwent lymphadenectomy rejected their allograft by 175 days. Animals that received DnonTx rejected their allografts by day 70.

CONCLUSION

Controlled delivery of TAC directly within the allograft (with a single TAC disk) effectively inhibits rejection and prolongs VCA allograft survival, while mitigating the complications of systemic immunosuppression. There was a survival benefit of delivering TAC within the allograft as compared to a remote site. We believe this approach of local drug delivery has significant implications for drug administration in transplantation.

Phellinus linteus Grown on Germinated Brown Rice Inhibits IgE-Mediated Allergic Activity through the Suppression of FcεRI-Dependent Signaling Pathway In Vitro and In Vivo

Phellinus linteus (PL) has been used as a traditional herbal medicine owing to its immune regulatory activity. Previous studies reported that PL grown on germinated brown rice (PBR) exerted immunomodulatory, anticancer, and anti-inflammatory activities. However, role of PBR on type I hypersensitive reactions has not been studied yet. We found that PBR contained more polyphenolic compounds than PL extract. Among fractions, PBR butanol fraction (PBR-BuOH) significantly contained the most amounts of total polyphenolic contents compared with all extracts or fractions. In this study, anti-allergic activity of PBR-BuOH was examined using in vitro and in vivo models of immunoglobulin E/antigen- (IgE/Ag-) stimulated allergy. The inhibitory activity of degranulation was higher in PBR-BuOH (IC₅₀ 41.31 ± 0.14 μg/mL) than in PL-BuOH (IC₅₀ 108.07 ± 8.98 μg/mL). We observed that PBR-BuOH suppressed calcium influx and the level of TNF-α and IL-4 mRNA expression in a dose-dependent manner. The phosphorylation of Fyn, Gab2, PI3K, Syk, and IκB protein is reduced by PBR-BuOH. Oral administration of PBR-BuOH inhibited allergic reactions including the extravasation of Evans blue dye, ear swelling, and infiltration of immune cells in mice with passive cutaneous anaphylaxis (PCA). These findings suggest that PBR-BuOH might be used as a functional food, a health supplement, or a drug for preventing type I hypersensitive allergic disease.

Synthesis of poly(lactide-co-glycerol) as a biodegradable and biocompatible polymer with high loading capacity for dermal drug delivery

Due to the low cutaneous bioavailability of tacrolimus (TAC), penetration enhancers are used to improve its penetration into the skin. However, poor loading capacity, non-biodegradability, toxicity, and in some cases inefficient skin penetration are challenging issues that hamper their applications for the dermal TAC delivery. Here we present poly(lactide-co-glycerol) (PLG) as a water soluble, biodegradable, and biocompatible TAC-carrier with high loading capacity (14.5% w/w for TAC) and high drug delivery efficiencies into the skin. PLG was synthesized by cationic ring-opening copolymerization of a mixture of glycidol and lactide and showed 35 nm and 300 nm average sizes in aqueous solutions before and after loading of TAC, respectively. Delivery experiments on human skin, quantified by fluorescence microscopy and LC-MS/MS, showed a high ability for PLG to deposit Nile red and TAC into the stratum corneum and viable epidermis of skin in comparison with Protopic® (0.03% w/w, TAC ointment). The cutaneous distribution profile of delivered TAC proved that 80%, 16%, and 4% of the cutaneous drug level was deposited in the stratum corneum, viable epidermis, and upper dermis, respectively. TAC delivered by PLG was able to efficiently decrease the IL-2 and TSLP expressions in human skin models. Taking advantage of the excellent physicochemical and biological properties of PLG, it can be used for efficient dermal TAC delivery and potential treatment of inflammatory skin diseases.

Mast cell stabilisers

Mast cells play a critical role in type 1 hypersensitivity reactions. Indeed, mast cell mediators are implicated in many different conditions including allergic rhinitis, conjunctivitis, asthma, psoriasis, mastocytosis and the progression of many different cancers. Thus, there is intense interest in the development of agents which prevent mast cell mediator release or which inhibit the actions of such mediators once released into the environment of the cell. Much progress into the design of new agents has been made since the initial discovery of the mast cell stabilising properties of khellin from Ammi visnaga and the clinical approval of cromolyn sodium. This review critically examines the progress that has been made in the intervening years from the design of new agents that target a specific signalling event in the mast cell degranulation pathway to those agents which have been developed where the precise mechanism of action remains elusive. Particular emphasis is also placed on clinically used drugs for other indications that stabilise mast cells and how this additional action may be harnessed for their clinical use in disease processes where mast cells are implicated.

Tryptase and protease-activated receptor-2 stimulate scratching behavior in a murine model of ovalbumin-induced atopic-like dermatitis

The aim of the current study was to investigate the involvement of tryptase and protease-activated receptor-2 (PAR2) in the pathogenesis of itch using a recently developed murine model of atopic dermatitis (AD) elicited by epicutaneous sensitization with ovalbumin (OVA). We also examined whether tacrolimus exerts an antipruritic effect. Epicutaneous sensitization of BALB/c mice with OVA led to a significant increase in the number of scratches. Notably, PAR2 mRNA and protein levels as well as cutaneous levels of tryptase were significantly enhanced in epicutaneously sensitized mice. Pretreatment with the protease inhibitor, leupeptin, PAR2 antibody, and tacrolimus significantly reduced the number of degranulated mast cells and tryptase content, and consequently alleviated scratching behavior. Cetirizine (10mg/kg) exerted a significant inhibitory effect on the scratching behavior of mice, but did not affect the number of degranulated mast cells and induction of tryptase. Our results collectively suggest that tryptase and PAR2 are involved in OVA allergy-induced scratching behavior.

Evaluation of Effect of Topical Tacrolimus Treatment on Herpetic Stromal Keratitis in a Rat Model

OBJECTIVES

To investigate the effectiveness of topical tacrolimus treatment on herpetic stromal keratitis (HSK) in a rat model.

METHODS

The development of HSK was monitored for 14 days after the inoculation of rats with herpes simplex type 1 virus. Rats that developed HSK were divided into four groups as follows: (1) topical antiviral treatment (control), (2) topical antiviral and 1% prednisolone acetate, (3) topical antiviral and 0.03% tacrolimus ointment, and (4) topical antiviral plus 0.1% tacrolimus ointment. After 14 days of treatment, the severity levels of HSK were scored and compared with the levels before the treatment. The expression of CD3, CD4, and CD8 was evaluated by flow cytometry. The development of the disease was evaluated clinically and histologically.

RESULTS

Significant improvement in vascularization was observed in the groups with the drug treatment in addition to the antiviral agent (P<0.05), but there was no obvious difference within groups 2, 3, and 4 in the vascularization severity. The regression of corneal edema was 8.05%±6% in group 1, 25.17%±14.55% in group 2 (P=0.01), 36.40%±21.69% in group 3 (P=0.03), and 46.39%±14.96% in group 4 (P=0.00). A significant decrease in the number of inflammatory cells in the groups with the drug treatment was evaluated by immunohistochemical staining and confirmed by flow cytometry analysis.

CONCLUSIONS

Topical tacrolimus treatment caused a significant decrease in corneal vascularization accompanied by a lower number of inflammatory cells in the experimental HSK corneal edema model. Therefore, topical tacrolimus has the potential to be used in the treatment of HSK.

Anti-IL-31 receptor antibody is shown to be a potential therapeutic option for treating itch and dermatitis in mice

BACKGROUND AND PURPOSE

IL-31, which is described as a pruritogenic cytokine, is linked to the itching that is associated with allergic and non-allergic eczema, but the precise pruritogenic mechanism of IL-31 and its potential as a therapeutic target for atopic dermatitis (AD) have not been determined.

EXPERIMENTAL APPROACH

We investigated the effects of existing drugs on the scratching behaviour induced by an i.v. injection of IL-31 to clarify whether IL-31 induced pruritus indirectly. In addition, we studied the effects of an anti-IL-31 receptor α subunit (anti-IL-31 receptor α) neutralizing antibody on chronic pruritus-inducing dermatitis in an AD-like model to determine whether IL-31 not only induces scratching behaviour, but is also the causative factor in an AD phenotype.

KEY RESULTS

The scratching behaviour induced by an i.v. injection of IL-31 was inhibited by pretreatment with an anti-IL-31 receptor α-neutralizing antibody. In contrast, it was not inhibited significantly by a non-sedative antihistamine (terfenadine), immunosuppressants (dexamethasone and tacrolimus), or a μ-opioid receptor antagonist (naloxone). The anti-IL-31 receptor α-neutralizing antibody reduced the ear swelling and dermatitis score in a chronic pruritus-inducing AD-like model. Moreover, treatment with the anti-IL-31 receptor α-neutralizing antibody showed therapeutic effects on the dermatitis even if it was injected after the disease had developed.

CONCLUSIONS AND IMPLICATIONS

Anti-IL-31 receptor α is a potential novel therapeutic approach for escaping from the itch-scratch cycle and also a treatment for dermatitis in AD.

Human mast cell degranulation and preformed TNF secretion require mitochondrial translocation to exocytosis sites: relevance to atopic dermatitis

BACKGROUND

Mast cells derive from hematopoietic cell precursors and participate in tissue allergic, immune, and inflammatory processes. They secrete many mediators, including preformed TNF, in response to allergic, neuropeptide, and environmental triggers. However, regulation of mast cell degranulation is not well understood.

OBJECTIVE

We investigated the role of mitochondrial dynamics in degranulation of human cultured mast cells.

METHODS

Human umbilical cord blood-derived mast cells (hCBMCs) and Laboratory of Allergic Diseases 2 (LAD2) mast cells were examined by confocal and differential interference contrast microscopy during activation by IgE/antigen and substance P (SP). Mast cells in control and atopic dermatitis (AD) skin were evaluated by transmission electron microscopy. LAD2 cells were pretreated with mitochondrial division inhibitor, a dynamin-related protein 1 (Drp1) inhibitor, and small interfering RNA for Drp1, which is necessary for mitochondrial fission and translocation. Calcineurin and Drp1 gene expression was analyzed in stimulated LAD2 cells and AD skin biopsies.

RESULTS

Stimulation of hCBMCs with IgE/antigen or LAD2 cells with SP leads to rapid (30 minutes) secretion of preformed TNF. Degranulation is accompanied by mitochondrial translocation from a perinuclear location to exocytosis sites. Extracellular calcium depletion prevents these effects, indicating calcium requirement. The calcium-dependent calcineurin and Drp1 are activated 30 minutes after SP stimulation. Reduction of Drp1 activity by mitochondrial division inhibitor and decrease of Drp1 expression using small interfering RNA inhibit mitochondrial translocation, degranulation, and TNF secretion. Mitochondrial translocation is also evident by transmission electron microscopy in skin mast cells from AD biopsies, in which gene expression of calcineurin, Drp1, and SP is higher than in normal skin.

CONCLUSION

Human mast cell degranulation requires mitochondrial dynamics, also implicated in AD.

The impact of tacrolimus on vascular endothelial growth factor in experimental corneal neovascularization

PURPOSE

To investigate the impact of tacrolimus on vascular endothelial growth factor (VEGF) in experimental corneal neovascularization (NV) immunohistochemically.

MATERIAL AND METHODS

Five groups of seven Wistar albino rats were formed. A silver nitrate cauterization technique was used to induce corneal NV in the study groups, excluding Group 1 (Control Group). Rats in group 1 did not receive any treatment. Rats in group 2 (sham 1) were administered 1 ml of saline intraperitoneally once a day and those in group 3 (sham 2) received one drop of saline four times a day. Rats in group 4 were administered 0.3 mg/kg tacrolimus intraperitoneally once a day. For group 5, 0.3 mg/ml tacrolimus was installed four times a day. Digital photography for each cornea was performed and the percentage area of the NV on the total corneal surface was calculated. The intensity of VEGF immunostaining in the epithelial, the stromal, and endothelial layers was performed in a semi quantitative fashion.

RESULTS

The mean percentages of the neovascularized areas of intraperitoneally and topically tacrolimus-treated groups were lesser than those of the sham groups (p = 0.002, p = 0.038, respectively). The mean intensity of the epithelial VEGF immunostaining of the intraperitoneally tacrolimus-treated group was less than that of its sham group (p = 0.002), while the mean intensity of the stromal VEGF staining of the topically tacrolimus-treated group was lesser than that of its sham group (p = 0.042). The intensities of the endothelial VEGF immunostaining of the intraperitoneally and topically tacrolimus-treated groups were less than those of the sham groups (p = 0.038, p = 0.032).

CONCLUSION

Systemic and topical administration of tacrolimus may be beneficial in the prevention of corneal NV because of its effect on VEGF.

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.

Tacrolimus hydrate ointment inhibits skin plasma extravasation in rats induced by topical m-xylene but not capsaicin

Tacrolimus ointment is used to treat various chronic inflammatory skin diseases. However, the effect of this ointment on acute neurogenic inflammation in the skin remains to be fully elucidated. Topical capsaicin and m-xylene produce tachykinin release from sensory nerves in the skin, resulting in skin plasma leakage. We investigated the effect of tacrolimus ointment (0.1%) on skin microvascular leakage induced by topical capsaicin (10 mM) and m-xylene (neat), and intracutaneous compound 48/80 (c48/80) (10 microg/ml, 50 microl/site) in two groups of rats pretreated with excessive capsaicin or its vehicle. The amount of leaked Evans blue dye reflected skin plasma leakage. Capsaicin, m-xylene or c48/80 was applied to the shaved abdomens of rats 8 h after topical application of tacrolimus ointment or its base. Desensitization with capsaicin reduced the skin response to capsaicin and m-xylene by 100% and 65%, respectively, but not to c48/80. Tacrolimus ointment significantly inhibited the skin response induced by m-xylene and c48/80, regardless of pretreatment with capsaicin. However, topical tacrolimus did not influence the skin response induced by capsaicin. We also evaluated whether topical capsaicin and m-xylene, and intracutaneous c48/80 cause mast cell degranulation in skin treated with tacrolimus. Mast cell degranulation was microscopically assessed. Topical tacrolimus only significantly suppressed degranulation induced by m-xylene and c48/80. Our data shows that tacrolimus ointment partially inhibits plasma leakage and mast cell degranulation in rat skin induced by m-xylene and c48/80 but not capsaicin, suggesting that the inhibitory effect is not associated with a reduction in neurogenic-mediated mechanisms.

The safety of tacrolimus ointment for the treatment of atopic dermatitis: a review

Tacrolimus ointment is a topical calcineurin inhibitor (TCI) that was developed specifically for the treatment of atopic dermatitis (AD). It is one of the most extensively tested dermatological products, with more than 19 000 patients (including approximately 7600 children) having participated in the tacrolimus ointment clinical development programme. Recent regulatory reviews have focused on the potential risk of malignancy with TCIs, based on their mode of action and the effects of systemic tacrolimus when given to transplant recipients. Studies have shown, however, that the systemic absorption of tacrolimus when applied topically is very low, with blood concentrations being below the level of quantification in most patients. Moreover, TCIs are not associated with a decrease in immunocompetence in the skin and there is no increase in the incidence of infections with long-term treatment. More than 5.4 million prescriptions for tacrolimus ointment have been issued worldwide, with no evidence of an increased risk of malignancy in adults or children compared with the general population. Similarly, epidemiological studies have failed to demonstrate an increased incidence of skin cancer in patients using TCIs. The most common adverse events (AEs) that occur with tacrolimus ointment treatment are transient application-site reactions, such as burning or pruritus. These complications are related to disease severity, and decrease in frequency over time as AD improves. The incidence of nonapplication-site AEs does not increase with long-term treatment, and most such events occurring in clinical trials were considered to be unrelated to therapy. Although it is important that clinicians are aware of the recent changes in product labelling, extensive clinical trials continue to show that tacrolimus ointment is well tolerated, and is generally an effective therapy for suitable patients with AD.

Pharmacological characterization of a chronic pruritus model induced by multiple application of 2,4,6-trinitrochlorobenzene in NC mice

Female NC/Jic mice were sensitized and challenged repeatedly at 48 h intervals for 10 and 30 days by painting 1% 2,4,6-trinitrochlorobenzene (TNCB) on both ears. Mice challenged with TNCB for 30 days developed an inflammatory dermatitis with high immunoglobulin E (IgE) titer. Histological analysis with acidic Toluidine Blue staining revealed that dermal mast cells markedly differentiated and intensely degranulated, consistent with a dramatic increase in scratching behavior. A significant increase in total scratching events could be observed in mice treated with TNCB for a short period of 10 days. Extending the term of TNCB application to 30 days, the IgE titer and number of mast cells elevated significantly, and thus various drugs were evaluated pharmacologically by using the mice treated with TNCB for 30 days. Terfenadine and cyproheptadine attenuated the chronic scratching behavior. Tacrolimus and dexamethasone were less effective and cromolyn showed no effect. In addition, terfenadine and tacrolimus suppressed the degranulation of mast cells. The present chronic scratching model could be suitable to evaluate drugs effective for suppression of mast cell differentiation and degranulation by irritation, and may represent a promising tool to develop new drugs for inflammatory pruritus associated with, for example, atopic dermatitis.

Dexamethasone suppresses histamine synthesis by repressing both transcription and activity of HDC in allergic rats

BACKGROUND

Histamine synthesized by histidine decarboxylase (HDC) from L-histidine is a major chemical mediator in the development of nasal allergy which is characterized by nasal hypersensitivity. However the regulatory mechanism of histamine synthesis by HDC remains to be elucidated. The objectives of the present study were to examine the changes of histamine content, HDC activity and HDC mRNA expression in the nasal mucosa of allergy model rats sensitized by the exposure to toluene diisocyanate (TDI) and to investigate the effect of dexamethasone on the above mentioned allergic parameters.

METHODS

Rats were sensitized and provocated by TDI and the nasal allergy-like behaviors were scored during a 10 minute period after provocation. Histamine content and HDC activity in the nasal mucosa were determined using fluorometric high performance liquid chromatography. The expression of HDC mRNA in nasal mucosa was determined using real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

In TDI-sensitized rats, nasal allergy-like behaviors such as sneezing and watery rhinorrhea were induced. Histamine content, HDC activity and HDC mRNA expression in nasal mucosa were also significantly increased after TDI provocation. Pretreatment with dexamethasone significantly suppressed nasal allergy-like behaviors, up-regulation of histamine content, HDC activity and HDC mRNA induced by TDI in TDI-sensitized rats.

CONCLUSIONS

These findings indicate that increased synthesis of histamine through up-regulation of HDC gene expression and HDC activity in nasal mucosa plays an important role in the development of nasal hypersensitivity. Repression of HDC gene expression and HDC activity by dexamethasone may underlie its therapeutic effect in the treatment of allergy.

Cytokine and Anti-Cytokine Therapies for Psoriasis and Atopic Dermatitis

Since the discovery of cytokines as key mediators in inflammation, targeting the cytokine network has represented a promising therapeutic approach. Psoriasis and atopic dermatitis, as T cell-mediated diseases with a strong cytokine component and a high unmet medical need, have moved into the focus of experimental therapies. Whereas pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha are overexpressed in both diseases, a type 1 cytokine pattern predominates in psoriasis and a type 2 cytokine pattern is of pathophysiological importance at least in the initial stages of atopic dermatitis. Strategies for intervention into the cytokine network have included antagonism of pro-inflammatory cytokines (e.g. TNFalpha, interleukin [IL]-1, IL-8, IL-12, IL-18, IL-23) with neutralizing antibodies and soluble receptors, application of recombinant cytokines (e.g. IL-4, IL-10, IL-11, interferon [IFN]-gamma) to shift the cytokine balance, and administration of small molecules to modulate cytokine expression or signaling. Results from the clinic have led to novel therapeutic options as well as a better understanding of the pathophysiology of inflammatory skin diseases. This review highlights the various therapeutic strategies, results from the clinic (that are in some cases preliminary), and insights that can be drawn from the more advanced clinical studies and the use of approved cytokine-directed therapies.

The mode of topical immunomodulators in the immunological network of atopic dermatitis

For a long time, therapeutic strategies of atopic dermatitis (AD) have been dominated by the application of local or systemic steroids or other immunosuppressive agents, which have been limited by their potential for unwanted local or systemic side effects. Recently, the use of a new generation of topical nonsteroidal, immunomodulatory drugs has revolutionized the therapeutic options of this often recalcitrant allergic-inflammatory skin disease. Research work has focused on the identification of the exact mode of action and the immune specificities of the so-called 'topical immunomodulators' (TIMs) such as tacrolimus and pimecrolimus in AD. In addition to the previous findings about the mode of action of TIMs on T cells, other target cells of TIMs such as keratinocytes, mast cells, eosinophils and dendritic cells have been identified recently as potential therapeutic targets. In this overview, we provide a research update about the anti-inflammatory and anti-allergic properties of TIMs on effector cells of AD that may be involved in the complex pathophysiology of AD.

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.

Successful treatment of eosinophilic pustular folliculitis with topical tacrolimus

We present two cases of Eosinophilic pustular folliclulitis (EPF) who were successfully treated with topical tacrolimus. Indomethacin is the most frequently used agent for the treatment of EPF, however, tacrolimus ointment may become the treatment of choice for patients with EPF.

Dexamethasone Suppresses Antigen-Induced Activation of Phosphatidylinositol 3-Kinase and Downstream Responses in Mast Cells

Dexamethasone and other glucocorticoids suppress FcepsilonRI-mediated release of inflammatory mediators from mast cells. Suppression of cytokine production is attributed to repression of cytokine gene transcription but no mechanism has been described for the suppression of degranulation. We show that therapeutic concentrations of dexamethasone inhibit intermediate signaling events, in particular the activation of phosphatidylinositol (PI)3-kinase and downstream signaling events that lead to degranulation in rat basophilic leukemia 2H3 cells. This inhibitory action is mediated via the glucocorticoid receptor and is not apparent when cells are stimulated via Kit in a mouse bone marrow-derived mast cell line. The primary perturbation appears to be the failure of the regulatory p85 subunit of PI3-kinase to engage with the adaptor protein Grb2-associated binder 2 leading to suppression of phosphorylation of phospholipase Cgamma2, the calcium signal, and degranulation. Suppression of PI3-kinase activation by dexamethasone may also contribute to reduced cytokine production because the PI3-kinase inhibitor LY294002, like dexamethasone, inhibits Ag-induced transcription of cytokine genes as well as degranulation.

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.

Synergistic effects of a novel nanoporous stent coating and tacrolimus on intima proliferation in rabbits

To overcome the problem of in-stent restenosis, the concept of local delivery of antiproliferative or immunosuppressive drugs has been introduced into interventional cardiology. Local drug delivery can be achieved by drug-eluting stents coated with polymer surfaces used for controlled drug release. However, several polymer coatings have shown an induction of inflammatory response and increased neointima formation. In the present study, the effect of a new inorganic ceramic nanoporous aluminum oxide (Al(2)O(3)) coating on neointima proliferation and its suitability as a carrier for the immunosuppressive drug tacrolimus have been investigated. 316 L stainless steel coronary stents were coated with a 500 nm thin nanoporous aluminum oxide layer. This ceramic nanolayer was used as a carrier for tacrolimus. Bare stents (n = 6), ceramic coated stents (n = 6), and ceramic coated stents loaded with 60 (n = 7) and 120 mug (n = 6) tacrolimus were implanted in the common carotid artery of New Zealand rabbits. The ceramic coating caused no significant reduction of neointimal thickness after 28 days. Loading the ceramic stents with tacrolimus led to a significant reduction of neointima thickness by 52% for 60 mug (P = 0.047) and 56% for 120 mug (P = 0.036) as compared to the bare stents. The ceramic coating alone as well as in combination with tacrolimus led to a reduced infiltration of lymphocytes and macrophages in the intima in response to stent implantation. Ceramic coating of coronary stents with a nanoporous layer of aluminum oxide in combination with tacrolimus resulted in a significant reduction in neointima formation and inflammatory response. The synergistic effects of the ceramic coating and tacrolimus suggest that this new approach may have a high potential to translate into clinical benefit.

Dexamethasone inhibits maturation, cytokine production and Fc epsilon RI expression of human cord blood-derived mast cells

BACKGROUND

Mast cells are responsible for eliciting the early phase and for contributing to the development of the late phase of allergic reactions, through the release of cytokines and other inflammatory mediators.

OBJECTIVE

To assess whether the glucocorticoid dexamethasone has a direct effect on mast cell progenitor maturation and on mature cord blood-derived mast cell properties.

METHODS

Mast cells were obtained by culturing human umbilical cord blood mononuclear cells with stem cell factor, IL-6 and prostaglandin E2. Mast cell numbers were assessed by Toluidine Blue staining and immunocytochemistry of tryptase positive cells. The expression of Fc epsilon RI, CD49d and c-kit was assessed by flow cytometry. Histamine release was determined by a radioenzymatic assay. Cys-LT, GM-CSF and TNF-alpha production and release were determined by ELISA.

RESULTS

Dexamethasone (10(-6) M-10(-9) M) time- and dose-dependently inhibited the maturation of the mast cell progenitors. Dexamethasone did not affect the basal expression of Fc epsilon RI, CD49d and c-kit, but it inhibited the IgE-dependent enhanced expression of Fc epsilon RI. Dexamethasone (10(-6) M-10(-9) M) had no significant effect on Fc epsilon RI-dependent histamine release or the synthesis and release of Cys-LT from the mature mast cells. However, pre-incubation of the mast cell cultures with dexamethasone for 1 h, prior to cross-linking of Fc epsilon RI, dose-dependently inhibited the production and secretion of both GM-CSF and TNF-alpha.

CONCLUSIONS

From these in vitro data we propose that glucocorticosteroids are effective drugs in the management of allergic inflammation due to their capacity to inhibit mast cell development, IgE-dependent Fc epsilon RI expression and mast cell production of GM-CSF and TNF-alpha.

Mechanisms of food allergy

The prevalence of food allergy continues to rise, particularly in 'westernized' societies; it has been linked to the 'hygiene hypothesis' and the increased diversity of food consumption worldwide. The pathogenic mechanisms and Th1/Th2 paradigm are being closely examined with respect to the occurrence of inflammatory and injury/repair responses at different mucosal sites. Genetically modified plants as potential food sources and allergenicity are current topics of controversy.