Therapeutic strategies for allergic diseases

Improving metabolic stability of phosphodiesterase-4 inhibitors containing a substituted catechol: prevention of reactive intermediate formation and covalent binding

A detailed study directed towards metabolic stability optimization of the alkoxy substituents on the catechol moiety of CDP-840 is reported. Replacement of the methoxy and cyclopentyloxy substituents by cyclobutyloxy and/or difluromethoxy groups resulted in the discovery of potent and selective PDE4 inhibitors where the formation of reactive metabolites that could covalently bind to microsomal protein was significantly reduced or eliminated.

Discovery of L-791,943: a potent, selective, non emetic and orally active phosphodiesterase-4 inhibitor

Structure-activity relationship studies directed toward improving the potency and metabolic stability of CDP-840 (3) resulted in the discovery of L-791,943 (11n) as a potent (HWB TNF-alpha = 0.67 microM) and orally active phosphodiesterase type 4 (PDE4) inhibitor. This compound, which bears a stable bis-difluoromethoxy catechol and a pendant hexafluorocarbinol, exhibited a long half-life in rat and in squirrel monkey. It is well tolerated in ferret with an emetic threshold greater than 30 mg/kg (po) and was found to be active in the ovalbumin-induced bronchoconstriction model in guinea pig and in the ascaris-induced bronchoconstriction models in sheep and squirrel monkey.

Anti-inflammatory activity of an extract of Petasites hybridus in allergic rhinitis

Previous studies have suggested that histamine and leukotrienes (LTs) play an important pathobiological role in IgE-mediated allergic diseases. In vitro studies suggested that an extract of Petasites hybridus (Ze339) blocks LT synthesis in monocytes and granulocytes. Petasins are considered to be the pharmacologically active fraction within Ze339. Patients suffering from allergic rhinitis received three times a day two tablets of Ze339 standardized to 8 mg petasins within a time period of 1 week. After 5 days of treatment, Ze339 significantly improved primary end points, which were day- and nighttime nasal symptoms. Nasal resistance, which was measured by rhinomanometry, gradually decreased as a consequence of Ze339 treatment reaching normal levels after 5 days (rhinomanometry: from 403.5+/-62.0 to 844.8+/-38.8 ml). Levels of inflammatory mediators in nasal fluids and serum were measured 90 min after drug administration every day in the morning. After 5 days of treatment, a significant reduction of histamine (from 153.7+/-32.1 to 53.0+/-8.4 pg/ml) and LT levels (LTB4: from 313.1+/-46.5 to 180.6+/-32.2 pg/ml; cysteinyl-LT: from 137.0+/-42.2 to 70.1+/-16.5 pg/ml) could be observed. Moreover, quality-of-life scores significantly improved. The drug had no effect on the distribution of lymphocyte subpopulations in the blood as well as on the capacity of blood leukocytes to generate cytokines and lipid mediators. These results suggest that Ze339 is effective in treating allergic rhinitis patients by decreasing levels of nasal inflammatory mediators.

Cytokine modulators as novel therapies for asthma

Cytokines play a critical role in orchestrating and perpetuating inflammation in asthmatic airways and several specific cytokine and chemokine inhibitors are now in development for the treatment of asthma. Inhibition of IL-4 with soluble IL-4 receptors has shown promising early results in asthma. Anti-IL-5 antibody is very effective at inhibiting peripheral blood and airway eosinophils but does not appear to be effective in symptomatic asthma. Inhibitory cytokines, such as IL-10, interferons, and IL-12 are less promising because systemic delivery produces intolerable side effects. Inhibition of TNF-alpha may be useful in severe asthma. Many chemokines are involved in the inflammatory response of asthma, and small-molecule inhibitors of chemokine receptors are in development. CCR3 antagonists are now in clinical development for the treatment of asthma. Because so many cytokines are involved in asthma, drugs that inhibit the synthesis of multiple cytokines may prove to be more useful. Several such classes of drug are now in clinical development, and the risk of side effects with these nonspecific inhibitors may be reduced by the inhaled route of delivery.

Immunological characterization of Echinococcus granulosus cyclophilin, an allergen reactive with IgE and IgG4 from patients with cystic echinococcosis

By immunological screening of a cDNA library derived from protoscoleces of Echinococcus granulosus with IgE from patients with cystic echinococcosis (CE) and allergic manifestations, we isolated a protein identical to E. granulosus cyclophilin. The protein, named EA21, has close homology with Malassezia furfur cyclophilin allergen (Mal f 6) and with human cyclophilin. Using immunoblotting (IB) with a polyclonal antibody specific to EA21, we identified E. granulosus cyclophilin both in protoscoleces and in sheep hydatid fluid. Of the 58 sera from patients with CE, 29 (50%) were IgE positive to EA21, whereas, despite the high sequence homology, none were IgE positive to Mal f 6 or human cyclophilin. Only 26 of the 58 patients (45%) had IgG specific to EA21, whereas all patients (100%) had IgG specific to Mal f 6 and human cyclophilin. IB analysis showed that serum IgE-binding reactivity to EA21 differed significantly in patients with and without allergic reactions (20 of 25, 80% versus nine of 33, 27%; P < 10(-4)). Conversely, five of the 25 patients who had CE-related allergic manifestations (20%) and 21 of the 33 who did not (63%) had specific IgG4 (P = 10(-3)) and total IgG to EA21. EA21 induced a proliferative response in 15 of 19 (79%) patients' PBMC regardless of the allergic manifestations, but it induced no IL-4 production. Overall, these findings suggest that E. granulosus cyclophilin is a conserved, constitutive, parasite protein that does not cross-react with cyclophilins from other organisms and is involved in the allergic symptoms related to CE.

Cyclooxygenases and prostaglandins: shaping up the immune response

The relevance of cyclooxygenases (COX)-1 and -2 and their products to inflammation, thrombosis and gastroprotection are well known. Their importance in the immune response was first recognized more than 25 years ago, but has only gained widespread attention recently. In this review, we attempt to integrate information on prostanoids and both the innate and acquired immune responses, including effects on leukocytes, antigen presenting cells, dendritic cells, T and B lymphocytes. Prostanoids may be relevant to immunotolerance, autoimmune disorders, transplantation, immunologic defense against tumors, acquired immunodeficiencies and viral infections. Insight into the role of prostanoids in immune function may afford novel therapeutic opportunities.

Pharmacological profile of a novel phosphodiesterase 4 inhibitor, 4-(8-benzo[1,2,5]oxadiazol-5-yl-[1,7]naphthyridin-6-yl)-benzoic acid (NVP-ABE171), a 1,7-naphthyridine derivative, with anti-inflammatory activities

We investigated the pharmacology of a new class of phosphodiesterase 4 (PDE4) inhibitor, 6,8-disubstituted 1,7-naphthyridines, by using 4-(8-benzo[1,2,5]oxadiazol-5-yl-[1,7]naphthyridin-6-yl)-benzoic acid (NVP-ABE171) as a representative compound and compared its potency with the most advanced PDE4 inhibitor, undergoing clinical trials, Ariflo [cis-4-cyano-4-(3-cyclopentyloxy-4-methoxyphenyl-r-1-cyclohexanecarboxylic acid)]. NVP-ABE171 inhibited the activity of phosphodiesterase 4A, 4B, 4C, and 4D with respective IC(50) values of 602, 34, 1230, and 1.5 nM. Ariflo was about 40 times less potent. In human cells, NVP-ABE171 inhibited the eosinophil and neutrophil oxidative burst, the release of cytokines by T cells, and the tumor necrosis factor-alpha release from monocytes, in the nanomolar range. Ariflo presented a similar inhibition profile but was 7 to 50 times less potent. In BALB/c mice challenged with lipopolysaccharide, NVP-ABE171 inhibited the airway neutrophil influx and activation with an ED(50) in the range of 3 mg/kg. Ariflo was inactive up to a dose of 10 mg/kg. In ovalbumin sensitized Brown Norway rats, NVP-ABE171 inhibited the lipopolysaccharide-induced airway neutrophil influx and activation (ED(50) of 0.2 mg/kg) and the ovalbumin-induced airway eosinophil influx and activation (ED(50) of 0.1 mg/kg). Ariflo was about 100 times less potent in both models. In the ovalbumin model, NVP-ABE171 had a duration of action of more than 24 h. NVP-ABE171 is a novel PDE4 inhibitor that shows activity both in vitro on human inflammatory cells and in vivo in animal models of lung inflammation. This compound class may have potential for the treatment of airway inflammatory conditions such as asthma and chronic obstructive pulmonary diseases.

Different glucocorticoids vary in their genomic and non-genomic mechanism of action in A549 cells

We have examined the effects of 12 glucocorticoids as inhibitors of A549 cell growth. Other than cortisone and prednisone, all the glucocorticoids inhibited cell growth and this was strongly correlated (r=0.91) with inhibition of prostaglandin (PG)E(2) formation. The molecular mechanism by which the active steroids prevented PGE(2) synthesis was examined and three groups were identified. Group A drugs did not inhibit arachidonic acid release but inhibited the induction of COX2. Group B drugs were not able to inhibit the induction of COX2 but inhibited arachidonic acid release through suppression of cPLA(2) activation. Group C drugs were apparently able to bring about both effects. The inhibitory actions of all steroids was dependent upon glucocorticoid receptor occupation since RU486 reversed their effects. However, group A acted through the NF-kappaB pathway to inhibit COX2 as the response was blocked by the inhibitor geldanamycin which prevents dissociation of GR and the effect was blocked by APDC, the NF-kappaB inhibitor. On the other hand, the group B drugs were not inhibited by NF-kappaB inhibitors or geldanamycin but their effect was abolished by the src inhibitor PP2. Group C drugs depended on both pathways. In terms of PGE(2) generation, there is clear evidence of two entirely separate mechanisms of glucocorticoid action, one of which correlates with NF-kappaB mediated genomic actions whilst the other, depends upon rapid effects on a cell signalling system which does not require dissociation of GR. The implications for these findings are discussed.

Neurogenic inflammation and particulate matter (PM) air pollutants

Exposure to a class of airborne pollutants known as particulate matter (PM) is an environmental health risk of global proportions. PM is thought to initiate and/or exacerbate respiratory disorders, such as asthma and airway hyper-responsiveness and is epidemiologically associated with causing death in the elderly and those with pre-existing respiratory, or cardiopulmonary disease. Plausible mechanisms of action to explain PM inflammation and its susceptible sub-population component are lacking. This review describes a series of published studies which indicate that PM initiates airway inflammation through sensory neural pathways, specifically by activation of capsaicin-sensitive vanilloid (e.g. VRI) irritant receptors. These acid-sensitive receptors are located on the sensory C nerve fibers that innervate the airways as well as on various immune and non-immune airway target cells. The activation of these receptors results in the release of neuropeptides from the sensory terminals that innervate the airways. Their interactions with airway target cells, result in signs of inflammation (e.g. bronchoconstriction, vasodilation, histamine release, mucous secretion etc.). Our data have linked the activation of the VR1 receptors to the surface charge carried on the colloidal particulates which constitute PM pollution. Related studies have examined how genetic and non-genetic factors modify the sensitivity of these irritant receptors and enhance the inflammatory responsiveness to PM. In summary, this review proposes a mechanism by which neurogenic elements initiate and sustain PM-mediated airway inflammation. Although neurogenic influences have been appreciated in normal airway homeostasis, they have not, until now, been associated with PM toxicity. The sensitivity of the sensory nervous system to irritants and its interactions with pulmonary target tissues, should encourage neuroscientists to explore the relevance of neurogenic influences to toxic disorders involving other peripheral target systems.

The enhanced effect of a hexameric deoxyriboguanosine run conjugation to CpG oligodeoxynucleotides on protection against allergic asthma

BACKGROUND

Oligodeoxynucleotides containing a CpG motif (CpG ODNs), as potent inducers of T(H)1 immunity, are considered promising candidates for immune modulation in asthma. We have previously demonstrated that conjugation of a hexameric deoxyriboguanosine run to the 3' terminus (3' dG(6)-run) of phosphodiester (PE) CpG ODNs enhanced their immuno-stimulatory activities in vitro.

OBJECTIVE

This study aimed to evaluate the effect of a 3' dG(6)-run conjugation to PE or phosphorothioate (PS) CpG ODNs on protection against murine allergic asthma in vivo.

METHODS

Balb/c mice were sensitized to ovalbumin by intraperitoneal injection with or without CpG ODNs (PS CpG ODNs, PE CpG ODNs, and those with 3' dG(6)-run) and subsequently challenged with ovalbumin. We evaluated airway hyperresponsiveness, eosinophil proportion in bronchoalveolar lavage fluid, airway inflammation, and ovalbumin-specific antibody responses.

RESULTS

The conjugation of a 3' dG(6)-run to PE CpG ODNs enhanced the production of IFN-gamma from ovalbumin-specific T(H) cells and prevented the development of asthma in terms of airway hyperresponsiveness, airway eosinophilia, and ovalbumin-specific IgE responses; these effects were comparable to those of PS CpG ODNs. Enhanced effects of the 3' dG(6)-run were also observed in PS CpG ODNs, though they were lower than those in PE CpG ODNs.

CONCLUSION

This study suggests that conjugation of a 3' dG(6)-run to CpG ODNs might provide an effective method for immune modulation of allergic asthma.

Phosphodiesterase type 4 inhibitor suppresses expression of anti-apoptotic members of the Bcl-2 family in B-CLL cells and induces caspase-dependent apoptosis

B cell chronic lymphocytic leukemia (B-CLL) is an incurable clonal disease which shows initial responsiveness to a number of chemotherapeutic drugs. However, in most patients the disease becomes resistant to treatment. Rolipram, a specific inhibitor of phosphodiesterase (PDE) type 4, the PDE predominantly expressed in B-CLL cells, has been shown to induce cAMP-dependent apoptosis in these cells. In the present study, we demonstrate that the extent of rolipram-induced apoptosis is similar to fludarabine-induced apoptosis in vitro. The combination of rolipram and fludarabine results in an enhancement in the number of apoptotic cells compared to apoptosis induced by either agent alone. Second, rolipram suppresses the expression of anti-apoptotic members of the Bcl-2 family and induces the pro-apoptotic protein Bax, thereby shifting the balance between pro- and anti-apoptotic members of the Bcl-2 family towards a pro-apoptotic direction. Finally rolipram-induced apoptosis is caspase-dependent. PDE 4 inhibitors are currently under investigation for chronic obstructive pulmonary disease and asthma in phase III clinical trials showing promising results with tolerable side-effects. In conclusion, by inducing apoptosis, by enhancing apoptosis induced by fludarabine, by suppressing Bcl-2, Bcl-X and by inducing Bax expression, PDE 4 inhibitors may add a new therapeutic option for patients with B-CLL.

Allergen-specific T cell reactivity in cord blood: the influence of maternal cytokine production

BACKGROUND

Successful pregnancy is dependent upon T helper (Th)2-type-dominated immunological responsiveness in gestation-associated compartments.

OBJECTIVE

In our study we observed the influence of the maternal Th2-associated cytokine pattern on the naive fetal T cell phenotype and asked if circulating Th2 cytokines of atopic mothers affects the Th1/Th2 differentiation of the fetus.

METHODS

Cord blood mononuclear cells (CBMC) and peripheral blood mononuclear cells (PBMC) of the corresponding mothers were isolated. The proliferative response of CBMC and PBMC to Betalactoglobulin (BLG) was assessed by liquid scintillation counting. The cytokines interferon (IFN)-gamma, and interleukin (IL)-5, IL-10 and IL-13 in the cell culture supernatants were measured using the ELISA technique. We then defined two subgroups based on maternal levels of specific IgE against aeroallergens: sensitized mothers (MA(+)) and their neonates (NMA(+)) (n = 18) and non-sensitized mothers (MA(-)) and their neonates (NMA(-)) (n = 29).

RESULTS

Nearly all mothers (98%) and neonates (92%) had a positive proliferation response after stimulation with BLG (mean stimulation index (10-90 percentile): neonates: 7 (2-15); mothers 14 (5-29)). In supernatants of BLG-stimulated cell cultures, sensitized mothers showed a significantly lower IFN-gamma concentration in comparison to non-sensitized mothers (MA(+) = 25; MA(-) = 123 IU/L; P < 0,05), whereas the neonates did not differ significantly (NMA(+) = 306; NMA(-) = 224 IU/L; n. s.). Nor was any difference found in the IL-13 concentration between the two groups of sensitized and non-sensitized mothers (MA(+) = 48; MA(-) = 125 pg/mL; n. s.). CBMC of neonates with a sensitized mother showed significantly higher IL-13 concentrations in response to BLG than neonates of non-sensitized mothers (NMA(+) = 1442, NMA(-) 738 pg/mL; P < 0.05). The IL-5 and IL-10 concentrations did not differ significantly within the neonatal and the maternal subgroups.

CONCLUSIONS

Our data suggests that maternal sensitization to allergens is associated with the reduced maternal production of the Th2 antagonist IFN-gamma and elevated production of the Th2 cytokine IL-13 in the offspring.

GM-CSF expression in pulmonary epithelial cells is regulated negatively by posttranscriptional mechanisms

Incubation of pulmonary A549 cells with D609, a phosphatidyl-choline specific phospholipase C (PC-PLC)-inhibitor, or the anti-oxidant, pyrrolidine dithiocarbamate (PTDC), markedly increased IL-1beta-induced GM-CSF elaboration. This effect was observed at the mRNA level and could be partially reproduced by the protein synthesis inhibitor, cycloheximide. Following the peak in GM-CSF mRNA, the mRNA half-life (t(1/2)) was 0.5-1 h. This was increased to around 3 h by cycloheximide, whilst following D609 or PDTC treatment there was essentially no degradation. These data suggest the existence of inhibitory pathways that posttranscriptionally regulate GM-CSF expression via new protein synthesis and D609- and PDTC-sensitive steps. These observations may have important clinical implications. First, drugs that target gene induction may also knock out these inhibitory pathways to lessen their effect. Second, defects in such pathways could lead to overexpression of cytokines or growth factors and contribute to the pathogenesis of inflammatory or proliferative diseases.

Preoperative prediction of postoperative edema and effusion in pediatric cardiac surgery by altered antigen expression patterns on granulocytes and monocytes

Postoperative edema and effusion (POEE) following cardiopulmonary bypass (CPB) surgery in children retards recovery and may aggravate postpericardiotomy (PPS), capillary leak syndrome (CLS), or multiorgan failure (MOF). Compared with complication-free children, POEE affected children have different preoperative serum levels of circulating cytokines and adhesion molecules. These levels may be used preoperatively to assess POEE, but their determination is time consuming, costly, and a substantial blood volume is required. Altered serum levels of cytokines and adhesion molecules also may be reflected in altered antigen expression on circulating blood leukocytes. The predictive potential of flow cytometric (FCM) leukocyte immunophenotyping was explored as a sensitive and fast method that required small blood samples. Blood samples taken 24 h preoperatively from 49 patients (3-18 years old) were stained with monoclonal antibodies for adhesion molecules (ICAM-1, LFA-1, Mac-1) or constitutive/activation markers (CD4, CD14, CD16, CD25, CD54, CD69, HLA-DR) and measured on a microbead calibrated FCM. Neutrophils, monocytes, and eosinophils from POEE patients express higher preoperative levels of LFA-1, monocytes, HLA-DR, and other activation markers (all P < 0.03). Over 89% of the patients were classified correctly by using two discriminant analysis methods (sensitivity, >76%; specificity, >86%; positive prediction, >80%; negative prediction, >83%). Granulocytes and monocytes of postoperative POEE patients exhibit significant preoperative immune activation, suggesting an increased risk for patients with atopic/allergic predisposition. Surgical trauma and CPB cause additional immune activation, leading to POEE by a summative response. Most patients at risk for POEE can be identified preoperatively by using data pattern analysis on FCM-derived parameters.

Differential inhibition of inflammatory effector functions by petasin, isopetasin and neopetasin in human eosinophils

BACKGROUND

Priming of eosinophils with granulocyte-macrophage colony-stimulating factor (GM-CSF) and subsequent stimulation with platelet-activating factor (PAF) or the anaphylatoxin C5a is associated with a rapid production of leukotrienes (LTs) and release of eosinophil cationic protein (ECP).

OBJECTIVE

This study was designed to determine the effects of the sesquiterpene esters petasin, isopetasin and neopetasin on LT generation and ECP release in eosinophils in vitro.

METHODS

The model of eosinophil activation described above was used to induce LT production and ECP release. Cells were incubated with petasins and control inhibitors prior to priming and stimulation. To analyse intracellular steps of eosinophil activation and determine potential drug targets, some key signalling events were studied. Activity of cytosolic phospholipase A2 (cPLA(2)) was measured by analysing the generation of arachidonic acid (AA). Translocation of 5-lipoxygenase (5-LO) was observed using immunofluorescence microscopy. Intracellular calcium concentrations [Ca2+]i were measured by a bulk spectrofluorometric assay.

RESULTS

Whereas all three compounds inhibited LT synthesis, ECP release from eosinophils was blocked by petasin only, but not isopetasin or neopetasin. Similarly, PAF- or C5a-induced increases in [Ca2+]i were completely abrogated by petasin only, whereas isopetasin and neopetasin had significant lower blocking efficacy. Moreover, only petasin, but not isopetasin or neopetasin, prevented increases in cPLA(2) activity and 5-LO translocation from the cytosolic compartment to the nucleus envelope in calcium ionophore-stimulated eosinophils.

CONCLUSION

These data suggest that different petasins may at least partially block different intracellular signalling molecules. To reduce LT synthesis, isopetasin and neopetasin may act at the level of or distal to 5-LO. In contrast, petasin may inhibit inflammatory effector functions in human eosinophils by disrupting signalling events at the level of or proximal to phospholipase Cbeta (PLCbeta), besides its potential inhibitory activity within mitogen-activated protein kinase (MAPK) and LT pathways.

Mast cell involvement in fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a catastrophic genetic disorder of progressive heterotopic ossification associated with dysregulated production of bone morphogenetic protein 4 (BMP4), a potent osteogenic morphogen. Postnatal heterotopic ossification in FOP is often heralded by hectic episodes of severe post-traumatic connective tissue swelling and intramuscular edema, followed by an intense and highly angiogenic fibroproliferative mass. The abrupt appearance, intense size, and rapid intrafascial spread of the edematous preosseous fibroproliferative lesions implicate a dysregulated wound response mechanism and suggest that cells and mediators involved in inflammation and tissue repair may be conscripted in the growth and progression of FOP lesions. The central and coordinate role of inflammatory mast cells and their mediators in tissue edema, wound repair, fibrogenesis, angiogenesis, and tumor invasion prompted us to investigate the potential involvement of mast cells in the pathology of FOP lesions. We show that inflammatory mast cells are present at every stage of the development of FOP lesions and are most pronounced at the highly vascular fibroproliferative stage. Mast cell density at the periphery of FOP lesional tissue is 40- to 150-fold greater than in normal control skeletal muscle or in uninvolved skeletal muscle from FOP patients and 10- to 40-fold greater than in any other inflammatory myopathy examined. These findings document mobilization and activation of inflammatory mast cells in the pathology of FOP lesions and provide a novel and previously unrecognized target for pharmacologic intervention in this extremely disabling disease.

Beta-galactofuranoside glycoconjugates on conidia and conidiophores of Aspergillus niger

Galactose in the furanoic conformation appears to be limited to bacteria and lower eukaryotes. Galactofuranoic (Galf)-containing glycoconjugates that occur in organisms pathogenic or allergenic to man are frequently antigenic and immunodominant. We have used an immunochemical approach, employing a monoclonal antibody that recognises Galf epitopes, to investigate the presence of Galf-containing glycoconjugates within conidia and conidiophores of Aspergillus niger. ELISA and immunofluorescence microscopy indicated that specific and saturable binding sites were found on both. Inhibition studies confirmed that this binding was to Galf-containing glycoconjugates. Interestingly, the conidiophore heads were particularly rich in these glycoconjugates. Western blotting identified a Galf glycoprotein of 150-200 kDa from disrupted conidia.

Experimental autoimmune myocarditis in A/J mice is an interleukin-4-dependent disease with a Th2 phenotype

Myocarditis in humans is often associated with an autoimmune process in which cardiac myosin (CM) is a major autoantigen. Experimental autoimmune myocarditis (EAM) is induced in mice by immunization with CM. We found that EAM in A/J mice exhibits a Th2-like phenotype demonstrated by the histological picture of the heart lesions (eosinophils and giant cells) and by the humoral response (association of IgG1 response with disease and up-regulation of total IgE). Blocking interleukin (IL)-4 with anti-IL-4 monoclonal antibody (mAb) reduced the severity of EAM. This reduction in severity was associated with a shift from a Th2-like to a Th1-like phenotype represented by a reduction in CM-specific IgG1; an increase in CM-specific IgG2a; an abrogation of total IgE response; a decrease in IL-4, IL-5, and IL-13; as well as a dramatic increase in interferon (IFN)-gamma production in vitro. Based on the latter finding, we hypothesized that IFN-gamma limits disease. Indeed, IFN-gamma blockade with a mAb exacerbated disease. The ameliorating effect of IL-4 blockade was abrogated by co-administration of anti-IFN-gamma mAb. Thus, EAM represents a model of an organ-specific autoimmune disease associated with a Th2 phenotype, in which IL-4 promotes the disease and IFN-gamma limits it. Suppression of IFN-gamma represents at least one of the mechanisms by which IL-4 promotes EAM.

Th2 responses without atopy: immunoregulation in chronic helminth infections and reduced allergic disease

The immune response to helminth infections has long been known to share key features with the allergic response. In particular, both are typified by enhanced T helper 2 (Th2) responses with high levels of interleukin-4 (IL-4), IL-5 and IL-13, accompanied by eosinophilia and abundant IgE production. Paradoxically, the geographical distribution of helminth parasitism and allergic disease is complementary rather than coincident. Thus, the question arises does the Th2 response to parasites protect or pre-empt the host from developing Th2-linked allergic manifestations? It is suggested that downregulatory immune mechanisms, which dampen the anti-parasite response, might benefit the host by blocking progression to atopic reactions. This is of relevance in explaining how the "hygiene hypothesis" might operate immunologically and in the design of therapeutics.

Regulation of mouse mast cell surface Fc epsilon RI expression by dexamethasone

It is now clear that the mast cell's functional response to IgE-dependent stimulation can be influenced significantly by the level of expression of the high-affinity IgE receptor (Fc epsilon RI) on the cell's surface. Thus, modulation of Fc epsilon RI surface expression represents a potentially important mechanism for regulating mast cell activity in allergic reactions. In this study, we examined whether a glucocorticoid, dexamethasone (DEX), can influence levels of mast cell Fc epsilon RI expression either in the presence or absence of IgE, an up-regulator of the mast cell surface Fc epsilon RI level. In the absence of IgE, DEX decreased the surface Fc epsilon RI levels in mouse peritoneal mast cells, mouse bone marrow-derived cultured mast cells and a mouse mast cell line, Cl.MC/C57.1. Moreover, DEX also partially suppressed the ability of IgE to enhance surface expression of Fc epsilon RI in these cells. Three different glucocorticoids, DEX, methylprednisolone and hydrocortisone, suppressed Fc epsilon RI expression in mast cells, whereas sex steroids, i.e. estradiol, progesterone and testosterone, did not, indicating that the Fc epsilon RI-suppressing effect is glucocorticoid specific. On the other hand, DEX did not affect levels of Fc epsilon RI alpha, beta or gamma mRNA, suggesting that its ability to decrease surface Fc epsilon RI reflects a post-transcriptional mechanism. Finally, DEX-treated mast cells showed a reduced degranulation response to antigenic stimulation through down-regulation of surface Fc epsilon RI expression in addition to DEX-induced changes in downstream signals. These results show that mast cell surface Fc epsilon RI expression is suppressed by glucocorticoids in both the presence and absence of IgE, and suggest that reduction of mast cell surface Fc epsilon RI levels may be one of the favorable anti-allergic actions of glucocorticoids.

Allergen-induced inflammation and the role of immunoglobulin E (IgE)

The prevalence of common allergic disorders such as asthma, allergic rhinitis, and atopic dermatitis has increased significantly in the past 30 years. The impact of these atopic diseases on the patient and the health care system is considerable: Allergic disorders are associated with a high degree of morbidity, which can profoundly impact patient quality of life and health care resource use. Existing strategies to treat allergic disorders beyond simple allergen avoidance focus on diminishing or eliminating the recurrent and/or persistent signs and symptoms that characterize the allergic response. A new strategy has been developed that uses antibodies directed against immunoglobulin E (IgE) to prevent it from binding to cells bearing its receptors and thus neutralizing the allergic response before it begins. These new agents reduce allergic responses in atopic individuals and improve their symptoms while reducing rescue medication and corticosteroid use in patients with allergic asthma or seasonal allergic rhinitis. Thus, anti-IgE antibodies represent proof that IgE plays a central role in allergic reactions and that anti-IgE therapy is a potentially effective treatment for allergic disease.

Fusarium solani major allergen peptide IV-1 binds IgE but does not release histamine

BACKGROUND

Fusarium solani (FS) is an important allergen source afflicting 4% of the nasobronchial allergy patients. Fus s I3596*, a 65 kDa major glycoprotein allergen of FS reacts with 95% fungus sensitive patients.

OBJECTIVES

To purify and characterize a potent peptide from Fus s I3596* which may be useful for therapeutic purposes.

METHODS

The 65 kDa protein was sequentially cleaved with trypsin and cyanogen bromide (CNBr). The cleaved products were purified on reverse phase high performance liquid chromatography (rpHPLC) column and functionally characterized by in vitro and in vivo methods for its IgE binding and histamine release.

RESULTS

The protein on cleavage showed 11 peaks (I to XI). Of these, peaks I, III, IV and V were highly allergenic as determined by IgE ELISA. These peaks were further purified and peptide IV-1 was most potent in comparison to other peptides by ELISA-inhibition. This peptide showed IgE binding but could not evoke intradermal response in Fusarium-sensitive patients. Heparinized blood challenged with peptide IV-1 does not release histamine. Preincubation of heparinized blood with peptide IV-1 and challenging with crude extract blocked histamine release in a dose dependent manner.

CONCLUSION

Peptide IV-1 binds to IgE but does not release histamine, demonstrating its potential use in therapy of Fusarium-allergic patients.

The roles of ATF3 in glucose homeostasis. A transgenic mouse model with liver dysfunction and defects in endocrine pancreas

Activating transcription factor 3 (ATF3) is a member of the ATF/cAMP-response element-binding protein family of transcription factors. It is a transcriptional repressor, and the expression of its corresponding gene is induced by stress signals in a variety of tissues, including the liver. In this report, we demonstrate that ATF3 is induced in the pancreas by partial pancreatectomy, streptozotocin treatment, and ischemia coupled with reperfusion. Furthermore, ATF3 is induced in cultured islet cells by oxidative stress. Interestingly, transgenic mice expressing ATF3 in the liver and pancreas under the control of the transthyretin promoter have defects in glucose homeostasis and perinatal lethality. We present evidence that expression of ATF3 in the liver represses the expression of genes encoding gluconeogenic enzymes. Furthermore, expression of ATF3 in the pancreas leads to abnormal endocrine pancreas and reduced numbers of hormone-producing cells. Analyses of embryos indicated that the ATF3 transgene is expressed in the ductal epithelium in the developing pancreas, and the transgenic pancreas has fewer mitotic cells than the non-transgenic counterpart, providing a potential explanation for the reduction of endocrine cells. Because ATF3 is a stress-inducible gene, these mice may represent a model to investigate the molecular mechanisms for some stress-associated diseases.

Screening of several Indonesian medicinal plants for their inhibitory effect on histamine release from RBL-2H3 cells

Twelve alcoholic extracts and 12 hexane extracts of plant materials selected on the basis of medicinal folklore for asthma treatment in Indonesia were studied for their activity in inhibiting histamine release from RBL-2H3 cells (rat basophilic leukemia cell line), a tumor analog of mast cells. The results of screening indicated that five alcoholic extracts (Plantago major leaves, Eucalyptus globulus leaves and fruit, Cinnamomum massoiae cortex, Vitex trifolia leaves) and two hexane extracts (Eucalyptus globulus leaves, Vitex trifolia leaves) inhibited IgE-dependent histamine release from RBL-2H3 cells. The inhibitory effects were found to be more than 80% for extract concentrations of 0.5 mg/ml. The results indicate that the extracts contain active compounds that inhibit mast-cell degranulation, and provide insight into the development of new drugs for treating asthma and/or allergic disease.

Role of petasin in the potential anti-inflammatory activity of a plant extract of petasites hybridus

A large production of leukotrienes (LTs) can be induced in human eosinophils or neutrophils by priming with granulocyte-macrophage colony-stimulating factor and subsequent stimulation with platelet-activating factor (PAF) or the anaphylatoxin C5a. Here, we investigated the effects of a plant extract of petasites hybridus (Ze339) and its isolated active sesquiterpene ester petasin in these two in vitro cell models. Zileuton, a 5-lipoxygenase inhibitor, was used as a positive control. All compounds inhibited both cysteinyl-LT synthesis in eosinophils and LTB(4) synthesis in neutrophils. In contrast, only Ze339 and petasin, but not zileuton, abrogated PAF- and C5a-induced increases in intracellular calcium concentrations. These data suggest that Ze339 and petasin may block, compared to zileuton, earlier signalling events initiated by G protein-coupled receptors in granulocytes, perhaps at the level of or proximal to phospholipase C(beta). Taken together, petasin appears to be one major active compound of petasites hybridus extract, since it demonstrates the same inhibitory activities on calcium fluxes and subsequent LT generation in both eosinophils and neutrophils as Ze339 does.

Novel drugs for treating asthma

The health burden of asthma is increasing globally at an alarming rate, providing a strong impetus for the development of new therapeutics, particularly drugs that may prevent development of the disease. Currently available inhaled bronchodilators and anti-inflammatory drugs are effective in most asthmatic patients, but this palliative therapy requires long-term daily administration. Despite considerable efforts by the pharmaceutical industry, it has been difficult to develop novel therapeutic agents, the leukotriene antagonists being the only new class of asthma treatments to be licensed in the past 30 years. It is clearly important to understand more about the underlying mechanisms of asthma and about how currently used drugs work before rational improvements in therapy can be expected. There are numerous therapies in clinical development that combat the inflammation found in asthma, specifically targeting eosinophils, IgE, adhesion molecules, cytokines (interleukin-4, -5, -13) and chemokines, inflammatory mediators, and cell signaling (kinase inhibitors). In particular, there is the obvious need for new therapy for severe asthma that is poorly controlled by high-dose corticosteroids as well as agents to counter acute emergency asthma. A long-term goal is to develop disease-modifying immunotherapy that could be introduced in childhood to alter the natural history of asthma. Thanks to the extensive efforts of the pharmaceutical industry, we can expect the introduction of a range of novel therapies for asthma in the near future.

Ceramide induction of COX-2 and PGE(2) in pulmonary A549 cells does not involve activation of NF-kappaB

Ceramide is generated by the hydrolysis of membrane sphingomyelin by sphingomyelinase (SMase) and is implicated in multiple signaling pathways, including activation of NF-kappaB. As NF-kappaB is pivotal in the expression of numerous genes associated with airway inflammation and asthma, the effects of ceramide and SMase were examined in human pulmonary A549 cells. Ceramide and SMase both induced cyclooxygenase (COX)-2 protein expression and stimulated PGE(2) release. However, neither ceramide nor SMase induced NF-kappaB DNA-binding, loss of IkappaBalpha, or NF-kappaB-dependent transcription. Both ceramide and SMase were efficient inducers of the extracellular regulated kinase (ERK), but not Jun N-terminal kinase (JNK) or p38 mitogen-activated protein kinase. Since ERK is implicated in arachidonic acid availability, these data partly explain the ability of ceramide to induce PGE(2) release. However, as ERK is not required for IL-1beta-dependent induction of COX-2, the mechanism of ceramide and SMase induction of COX-2 remains unclear.

T-helper type 2 cell-directed therapy for asthma

Asthma is a chronic inflammatory disease of the bronchial airways. Current research in humans and animals suggests that T-helper type 2 (Th2) cells and the cytokines they elaborate cause many of the pathophysiologic abnormalities characteristic of the disease. We review the evidence implicating Th2 cells in asthma and discuss the cellular and molecular mechanisms that control Th2 cell differentiation in the respiratory tract. Based on the steps in Th cell development, we discuss how traditional therapies can modulate Th2 cell function. Furthermore, we explore newer immunomodulatory strategies to inhibit Th2 cell effects, including therapies that may block Th2 cell differentiation, neutralize cytokines, and redirect immune responses towards Th1 and away from Th2.

New approaches to topical therapy

Despite the rapid and proven efficacy of topical corticosteroids, side-effects can limit their clinical usefulness. Topically active macrolide immunosuppressants such as ascomycin and tacrolimus appear to provide comparable therapeutic potency without significant local or adverse effects. Data from ongoing studies will be crucial in determining the safety of these agents in the long term, and also their place within the current therapeutic armamentarium available for patients with atopic dermatitis. Enzyme inhibitors of PLA(2) and PDE 4 currently in the very early stages of clinical development also show potential promise as additional alternative strategies to topical treatment and may perhaps act as steroid sparing agents. Having been in the therapeutic doldrums for years, topical management of atopic dermatitis is likely to show great changes in the very near future.

Activating and inhibitory signaling in mast cells: new opportunities for therapeutic intervention?

Immune responses are tightly controlled by the activities of both activating and inhibitory signals. At the cellular level, these signals are generated through engagement of membrane-associated receptors and coreceptors. The high-affinity IgE receptor FcepsilonRI is expressed on mast cells and basophils and, on cross-linking by multivalent antigen (allergen), stimulates the release of inflammatory mediators that induce acute allergic responses. Activation signals mediated by a variety of immune receptors (eg, B-cell receptor, T-cell receptor, and FcepsilonRI) are subject to negative regulation by a growing family of structurally and functionally related inhibitory receptors. Recent studies indicate that mast cells express multiple inhibitory receptors that may regulate FcepsilonRI-induced mast cell activation through similar mechanisms. The ability of inhibitory receptors to attenuate IgE-mediated allergic responses implicates them as potential targets for therapeutic intervention in the treatment of atopic disease. Indeed, coaggregation of activating and inhibitory receptors has been suggested as one possible mechanism to explain the beneficial effects of specific immunotherapy in the treatment of allergy. In this review we summarize the current knowledge of inhibitory receptors expressed in mast cells and the mechanisms through which they regulate mast cell function.

Mast cells can amplify airway reactivity and features of chronic inflammation in an asthma model in mice

The importance of mast cells in the development of the allergen-induced airway hyperreactivity and inflammation associated with asthma remains controversial. We found that genetically mast cell-deficient WBB6F(1)-W/W(v) mice that were sensitized to ovalbumin (OVA) without adjuvant, then challenged repetitively with antigen intranasally, exhibited much weaker responses in terms of bronchial hyperreactivity to aerosolized methacholine, lung tissue eosinophil infiltration, and numbers of proliferating cells within the airway epithelium than did identically treated WBB6F(1)-+/+ normal mice. However, W/W(v) mice that had undergone selective reconstitution of tissue mast cells with in vitro-derived mast cells of congenic +/+ mouse origin exhibited airway responses that were very similar to those of the +/+ mice. By contrast, W/W(v) mice that were sensitized with OVA emulsified in alum and challenged with aerosolized OVA exhibited levels of airway hyperreactivity and lung tissue eosinophil infiltration that were similar to those of the corresponding +/+ mice. Nevertheless, these W/W(v) mice exhibited significantly fewer proliferating cells within the airway epithelium than did identically treated +/+ mice. These results show that, depending on the "asthma model" investigated, mast cells can either have a critical role in, or not be essential for, multiple features of allergic airway responses in mice.

Asthma: where beyond steroids?

The prevalence of asthma is increasing dramatically despite major changes in monitoring and treatment of this disease. Currently available bronchodilators and anti-inflammatory drugs are effective in most patients, although these can have side effects and are mainly symptomatic. Many drugs are now in development for the treatment of asthma. Most of these new therapies are aimed at inhibition of the inflammatory components, with better safety profiles than steroids.

Experimental approaches to analysis of immune dysregulation in human allergic disease

Over the last 40 years, much attention has been directed towards identification of the immunologic, genetic and environmental factors that predispose towards development of allergic disease. An implicit assumption in many such studies is that clinical tolerance reflects from immunologic tolerance. Here we critically review the conceptual background and experimental data arguing for the alternative hypothesis that failure to develop atopic disease reflects the success of type 1 dominated immunity that constitutively impedes development of type 2 responses to environmental antigens, hence, clinical immediate hypersensitivity. We report that endogenous production of type 1 chemokines such as IP-10 by non-atopic individuals may play a substantive role in maintaining this putatively protective type 1 bias in non-atopic subjects. Polyclonal activators (superantigen TSST-1, anti-CD3, PHA) were used to activate distinct intracellular signaling pathways, inducing quantitatively different IFNgamma:IL-4 ratios in primary culture of human PBMC. In parallel, physiologic stimuli such as grass pollen or cat antigen were used to evaluate the impact of IP-10 on CD4 T cell dependant, chloroquine-sensitive cytokine synthesis. IFNgamma responses by non-atopic subjects were markedly increased in the presence of nM concentrations of rhIP-10 while type 2 cytokine synthesis remained unaffected. Optimal rIP-10 concentrations for promoting expression and maintenance of type 1 cytokine synthesis in vitro (0.1 to 10 ng/ml) were at or well below those generally used for chemotaxis (5 to 100 ng/ml). Collectively, our findings suggest a potential role for this T cell focused chemokine in maintaining the default type 1 responses usually caused to environmental antigens in non-atopic subjects. These may play a role in determining the relative susceptibility of individuals to develop atopic disease. Taken together with recent reports of other roles played by chemokines in shaping the nature of immune responses, the data suggest that constitutive, endogenous type 1 chemokine synthesis may play a homeostatic role in inhibiting development of atopic disease.

Failure of rIL-12 administration to inhibit established IgE responses in vivo is associated with enhanced IL-4 synthesis by non-B/non-T cells

Administration of rIL-12 offers a widely successful tactic for preferential induction of type 1 immune responses in vivo. Its use to modulate ongoing cytokine or effector responses has proven to be substantially more difficult. Immediate hypersensitivity is the most common human immunologic disease. Here, rIL-12 was administered to C57Bl/6 and outbred CD1 mice with ongoing ovalbumin (OVA)-specific IgE responses in an attempt to redirect established type 2 cytokine and antibody production. Despite use of a broad range of treatment protocols for >4 months following initial immunization, recall IgE responses were consistently unaffected. rIL-12-treated mice exhibited strong in vivo and in vitro IFN-gamma responses, increased approximately 40-fold relative to controls, but also markedly enhanced (15- to 20-fold) OVA-specific IL-4 production. CD4 T cell function was successfully transformed from a type 2- to a type 1-dominated pattern following long-term IL-12 administration in vivo, as measured by strongly reduced IL-4 and IL-10 responses in antigen-stimulated primary culture, and 5-fold reductions in the frequencies of IL-4- and IL-10-producing OVA-specific CD4 T cells. However, chronically rIL-12-treated mice exhibited increased numbers of non-B/non-T cells that when re-stimulated with specific allergen, produce IL-4 at levels 20-fold higher than did CD4 T cells while IL-13 responses are unaffected. Collectively, the data indicate that even effectively shifting CD4 T cell activation from a type 2- to a type 1-dominated response does not in itself lead to altered effector (IgE) responses upon antigen re-exposure.

The MAP kinase inhibitors, PD098059, UO126 and SB203580, inhibit IL-1beta-dependent PGE(2) release via mechanistically distinct processes

1. In common with human bronchial epithelial cells, pulmonary A549 cells release prostaglandin (PG) E(2) in response to pro-inflammatory cytokines. We have therefore used these cells to examine the effect of the selective mitogen activated protein (MAP) kinase inhibitors; PD098059, a mitogen activated and extracellular regulated kinase kinase (MEK) 1 inhibitor, UO126, a dual MEK1 & MEK2 inhibitor, and SB203580, a p38 MAP kinase inhibitor in the IL-1beta-dependent release of PGE(2). 2. Following IL-1beta treatment the extracellular regulated kinases (ERKs) and the p38 MAP kinases were rapidly phosphorylated. 3. PD09059, UO126 and SB203580 prevented IL-1beta-induced PGE(2) release at doses that correlated closely with published IC(50) values. Small or partial effects at the relevant doses were observed on induction of cyclo-oxygenase (COX) activity or COX-2 protein suggesting that the primary effects were at the level of arachidonate availability. 4. Neither PD098059 nor SB203580 showed any effect on IL-1beta-induced arachidonate release. We therefore speculate that the MEK1/ERK and p38 kinase cascades play a role in the functional coupling of arachidonate release to COX-2. 5. In contrast, UO126 was highly effective at inhibiting IL-1beta-dependent arachidonate release, implicating MEK2 in the activation of the PLA(2) that is involved in IL-1beta-dependent PGE(2) release. 6. We conclude that the MEK1, MEK2 and p38 MAP kinase inhibitors, PD098059, UO126 and SB203580, are highly potent in respect of inflammatory PG release. Finally, we conclude that these inhibitors act via mechanistically distinct processes, which may have anti-inflammatory benefits.

Understanding cytokines. Part II: Implications for nursing research and practice

Cytokines are small signaling proteins released from a variety of cells that influence virtually every aspect of growth and development and every host response to infection, injury, and inflammation. Because of their widespread and potent effects across the life span, cytokines without a doubt influence nursing research and practice. From physiological and adaptive effects of cytokines to cytokine-induced diseases, nurses and nursing care are involved. Part II of this review highlights a few of the many examples of cytokines functioning in response to infection and inflammation, during the processes of reproduction, and in a variety of pathophysiological states. Implications for nursing research and practice are emphasized.

New directions in allergic diseases: mechanism-based anti-inflammatory therapies

Advances in our understanding of allergic inflammation have led to the development of several novel anti-inflammatory drugs that target specific aspects of the inflammatory process. These treatments are based on improvements in existing therapies or on a better understanding of the cellular and molecular mechanisms involved in atopic diseases. Although most attention has been focused on asthma, treatments that inhibit the atopic disease process would have application to all atopic diseases, which often coincide. Specific agents that are now in development for the treatment of allergic inflammation include inhibitors of eosinophilic inflammation (eg, anti-IL-5, CCR3 antagonists, and very late antigen 4 inhibitors), drugs that may inhibit allergen presentation, and inhibitors of T(H)2 cells. More general anti-inflammatory approaches include novel cortico-steroids, phosphodiesterase inhibitors, and mitogen-activated protein kinase inhibitors. Most of the new therapies in development are aimed at inhibiting or suppressing components of the allergic inflammatory response, but in the future, there are possibilities for development of preventive and curative treatments.

The diverse potential effector and immunoregulatory roles of mast cells in allergic disease

Mast cells are of hematopoietic origin but typically complete their maturation in peripheral connective tissues, especially those near epithelial surfaces. Mast cells express receptors that bind IgE antibodies with high affinity (FcepsilonRI), and aggregation of these FcepsilonRI by the reaction of cell-bound IgE with specific antigens induces mast cells to secrete a broad spectrum of biologically active preformed or lipid mediators, as well as many cytokines. Mast cells are widely thought to be essential for the expression of acute allergic reactions, but the importance of mast cells in late-phase reactions and chronic allergic inflammation has remained controversial. Although it is clear that many cell types may be involved in the expression of late-phase reactions and chronic allergic inflammation, studies in genetically mast cell-deficient and congenic normal mice indicate that mast cells may be critical for the full expression of certain features of late-phase reactions and may also contribute importantly to clinically relevant aspects of chronic allergic inflammation. Moreover, the pattern of cytokines that can be produced by mast cell populations, and the enhancement of such cytokine production in mast cells that have undergone IgE-dependent up-regulation of their surface expression of FcepsilonRI, suggests that mast cells may contribute to allergic diseases (and host defense) by acting as immunoregulatory cells, as well as by providing effector cell function.