Prostaglandin D2 and histamine during the immediate and the late-phase components of allergic cutaneous responses

DP1 receptor signaling prevents the onset of intrinsic apoptosis in eosinophils and functions as a transcriptional modulator

Prostaglandin (PG) D₂ is the ligand for the G-protein coupled receptors DP1 (D-type prostanoid receptor 1) and DP2 (also known as chemoattractant receptor homologous molecule, expressed on Th2 cells; CRTH2). Both, DP1 and DP2 are expressed on the cellular surface of eosinophils; although it has become quite clear that PGD₂ induces eosinophil migration mainly via DP2 receptors, the role of DP1 in eosinophil responses has remained elusive. In this study, we addressed how DP1 receptor signaling complements the pro-inflammatory effects of DP2. We found that PGD₂ prolongs the survival of eosinophils via a DP1 receptor-mediated mechanism that inhibits the onset of the intrinsic apoptotic cascade. The DP1 agonist BW245c prevented the activation of effector caspases in eosinophils and protected mitochondrial membranes from depolarization which-as a consequence-sustained viability of eosinophils. DP1 activation in eosinophils enhanced the expression of the anti-apoptotic gene BCL-X_L , but also induced pro-inflammatory genes, such as VLA-4 and CCR3. In HEK293 cells that overexpress recombinant DP1 and/or DP2 receptors, activation of DP1, but not DP2, delayed cell death and stimulated proliferation, along with induction of serum response element (SRE), a regulator of anti-apoptotic, early-response genes. We conclude that DP1 receptors promote the survival via SRE induction and induction of pro-inflammatory genes. Therefore, targeting DP1 receptors, along with DP2, may contribute to anti-inflammatory therapy in eosinophilic diseases.

Lipid Mediators of Allergic Disease: Pathways, Treatments, and Emerging Therapeutic Targets

Bioactive lipids are critical regulators of inflammation. Over the last 75 years, these diverse compounds have emerged as clinically-relevant mediators of allergic disease pathophysiology. Animal and human studies have demonstrated the importance of lipid mediators in the development of asthma, allergic rhinitis, urticaria, anaphylaxis, atopic dermatitis, and food allergy. Lipids are critical participants in cell signaling events which influence key physiologic (bronchoconstriction) and immune phenomena (degranulation, chemotaxis, sensitization). Lipid-mediated cellular mechanisms including: (1) formation of structural support platforms (lipid rafts) for receptor signaling complexes, (2) activation of a diverse family of G-protein coupled receptors, and (3) mediating intracellular signaling cascades by acting as second messengers. Here, we review four classes of bioactive lipids (platelet activating factor, the leukotrienes, the prostanoids, and the sphingolipids) with special emphasis on lipid synthesis pathways and signaling, atopic disease pathology, and the ongoing development of atopy treatments targeting lipid mediator pathways.

9α,11β-PGF2, a Prostaglandin D2 Metabolite, as a Marker of Mast Cell Activation in Bee Venom-Allergic Patients

Mast cell (MC) mediators, among them prostaglandin D₂ (PGD₂) and 9α,11β-PGF₂, PGD₂’s metabolite, play a key role in allergic reactions, including bee venom anaphylaxis (BVA). Assessment of these mediators has never been performed in BVA. The aim of the study was to assess the activation of MC during in vivo provocation with bee venom (BV) and to measure PGD₂ and 9α,11β-PGF₂ in the course of an allergen challenge. The second aim was to determine if assessment of these mediators could be useful for predicting adverse events during venom immunotherapy (VIT). In 16 BV-VIT patients and 12 healthy subjects, levels of PGD₂ and 9α,11β-PGF₂ were assessed during BV provocation by means of the skin chamber method. Chamber fluids, collected at 5 and 15 min, were analyzed for both mediators by gas chromatography mass spectrometry negative ion chemical ionization. BVA in comparison to non-allergic patients had a significantly higher ratio of 9α,11β-PGF₂ in allergen-challenged chambers to 9α,11β-PGF₂ in allergen-free chambers after 15 min of provocation (p = 0.039). Allergen challenge resulted in a significant increase of 9α,11β-PGF₂ levels between 5 and 15 min after provocation only in BVA patients (p < 0.05). Analysis of log-transformed PGD2 levels showed significant difference between changes in PGD₂ concentration between BVA and healthy subjects. No study patient developed adverse reactions during. 9α,11β-PGF₂ is actively generated during the early allergic response to BV. Skin chamber seems to be a promising, non-invasive and safe model of in vivo allergen provocation in BV-allergic patients. High or low levels of both mediators do not predict occurrence of adverse events during VIT.

A controlled study of 9alpha,11beta-PGF2 (a prostaglandin D2 metabolite) in plasma and urine of patients with bronchial asthma and healthy controls after aspirin challenge

BACKGROUND

Prostaglandin D(2) (PGD(2)) is the predominant cyclooxygenase product of mast cells, the number of which is increased in bronchial asthma. Release of PGD(2) might reflect mast cell activation and disordered function of the asthmatic lung.

OBJECTIVE

We sought to determine blood and urinary levels of 9alpha,11beta-PGF(2), a major stable PGD(2) metabolite in 2 well-defined phenotypes of asthma, aspirin-induced asthma (AIA) and aspirin-tolerant asthma (ATA), and in healthy control subjects and to study the effects of aspirin on PGD(2) release.

METHODS

Using gas chromatography/mass spectrometry, we determined plasma and urinary concentrations of 9alpha,11beta-PGF(2) at baseline in 131 stable asthmatic patients, 65 of whom had AIA and 66 of whom had ATA. Fifty healthy nonatopic subjects served as the control group. The measurements were also performed after an aspirin challenge in 26 of 65 patients with AIA and in 24 of 50 control subjects.

RESULTS

At baseline, patients with AIA had significantly higher plasma levels of 9alpha,11beta-PGF(2) than either patients with ATA or healthy subjects. A similar significant elevation of serum tryptase was observed in patients with AIA compared with patients with ATA and control subjects. Mean urinary 9alpha,11beta-PGF(2) values did not differ among the 3 groups. In patients with AIA, as opposed to healthy subjects, aspirin challenge invariably precipitated a clinical reaction, accompanied in most patients by a further rise in plasma levels of PGD(2) metabolite and tryptase.

CONCLUSIONS

In stable AIA, though not in ATA, there is a steady release of PGD(2) into the blood, accompanied by the release of tryptase. Aspirin enhances this reaction in most patients. Release of bronchoconstrictive PGD(2) might contribute to the severe clinical course of AIA.

Association of a new-type prostaglandin D2 receptor CRTH2 with circulating T helper 2 cells in patients with atopic dermatitis

Prostaglandin D2 is known to be the major prostanoid produced by allergen-activated mast cells, but its role in the formation of allergic diseases is not well established because of complexity of its receptor system and lack of appropriate inhibitors. We have recently identified a new-type prostaglandin D2 receptor, named CRTH2. Studies with normal subjects have shown that CRTH2 appears to be selectively expressed by T helper 2 cells but not T helper 1 cells among circulating CD4+ lymphocytes. The exact correlation between CRTH2 and T helper 2 cells in various disease settings and the impact of CRTH2-mediated prostaglandin D2 activities on various T helper 2 responses in vivo still remain to be elucidated, however. In this study, we investigated the correlation between CRTH2 and T helper 2 cells among circulating CD4+ lymphocytes in normal adults and patients with atopic dermatitis, a T-helper-2-involving disease. The results showed that virtually all CRTH2+CD4+ lymphocytes had a pure T helper 2 phenotype and formed not all but a large proportion of circulating T helper 2 cells for both normal and atopic dermatitis subjects. In chemotaxis assays, peripheral blood CRTH2+CD4+ lymphocytes were significantly attracted by prostaglandin D2 as well as by a typical T-helper-2-attracting chemokine, thymus and activation regulated chemokine, whereas they showed little chemotactic migration toward typical T-helper-1-attracting chemokines, macrophage inflammatory protein 1beta and interferon-gamma-inducible protein 10. Furthermore, in atopic dermatitis patients, a preferential increase of CRTH2+ cells was noted within the disease-related cutaneous lymphocyte-associated antigen-positive, but not the cutaneous lymphocyte-associated antigen-negative, CD4+ lymphocyte compartment. Our results suggest the involvement of the prostaglandin D2/CRTH2 system in both normal and pathogenic T helper 2 responses.

Quantitative analysis of T-cell receptor beta variable-gene usage in cutaneous late-phase reactions: implications for T-lymphocyte recruitment in cutaneous inflammation

To determine if functionally distinct T-lymphocyte (T cell) subsets accumulate in late-phase immunoglobulin E-mediated reactions (LPR), we quantitatively analyzed the immunophenotype and the T-cell receptor beta variable-gene (Vbeta) repertoire of T cells in cutaneous LPR. Peripheral blood and skin biopsies were obtained 6 or 24 h after sensitive subjects were challenged with intradermal injections of grass pollen allergen (Ag) and control (C) solution. The frequency of cells expressing CD3, CD4, CD8, CD45RO, and CD25/mm2 was determined by immunohistochemistry in nine subjects. Vbeta usage was assessed by reverse transcription-PCR in five of nine subjects. A significantly greater frequency of CD3(+) and CD45RO+ (memory) T cells was detected in Ag sites than in C sites at 24 h after challenge but not at 6 h. The frequency of activated (CD25(+)) and helper (CD4(+)) T cells appeared to be increased in Ag sites as well, though not significantly. Vbeta6 was the most commonly expressed Vbeta detected in Ag sites, but it was also detected in accompanying C sites. Vbeta2 was the most commonly expressed Vbeta detected in C sites. Sequence analysis in one case revealed Vbeta expression in a 6-h Ag site to be essentially polyclonal. Our findings suggest that memory T cells with Vbeta expression similar to that in normal skin accumulate in developing cutaneous LPR. The limited usage of Vbeta suggests a preferential recruitment or retention of reactive T cells from an endogenous subset of skin-homing T cells with its own skewed Vbeta repertoire.

Clinical comparison of histamine H1-receptor antagonist drugs

Nearly 40 million Americans have symptoms of upper respiratory allergies, making antihistamines among the most frequently used pharmacologic agents. Although there are mediators of allergic symptoms in addition to histamine, therapy for allergic rhinitis and urticaria has focused upon the use of antihistamines. The classic histamine H1-receptor antagonists, however, are not selective for the H1 site and produce a variety of dopaminergic, serotonergic, and cholinergic responses leading to considerable adverse effects in the central nervous system consequent to both their pharmacologic nonselectivity and their ability to penetrate the blood-brain barrier readily. The second-generation antihistamines were a major advance in the therapy of allergic rhinitis, because they do not penetrate the blood-brain barrier as rapidly and are also designed for greater specificity at H1-receptor. Given their greater selectivity for the H1-receptor, they cause fewer undesirable central nervous system actions, whereas their efficacy is similar to that of the classic antihistamines used in the treatment of allergic rhinitis. Selecting among these antihistamines for the treatment of allergic rhinitis has focused on their pharmacokinetics and adverse effect profiles. The potential cardiotoxic effects of some antihistamines when their metabolism is inhibited requires caution in prescribing these agents. The antiallergic and antiasthmatic effects of several newer antihistamines are being explored. For the clinician, making the therapeutic decision among H1-receptor antagonists requires a comprehensive knowledge of their diverse effects.

Inflammatory mechanisms in the passive cutaneous anaphylactic reaction in the rabbit: evidence that novel mediators are involved

1. We have examined the mechanisms of local oedema formation in the passive cutaneous anaphylactic (PCA) reaction in the rabbit. 2. IgE-containing antiserum was injected i.d. and allowed to sensitize skin sites for periods up to 240 h. Antigen (bovine gamma globulin) was injected i.d. or i.v. and local oedema formation assessed by the accumulation of i.v. injected 125I-labelled rabbit serum albumin. Potential inhibitors were mixed with antigen prior to i.d. injection or were administered i.v. 3. Maximum oedema formation was observed when a sensitization period of 48-72 h was used. Oedema formation in the PCA reaction was of short duration with a t 1/2 of approximately 15 min. No evidence of late oedema formation (up to 6 h) was found. 4. Local oedema formation in the PCA was reduced by indomethacin suggesting that vasodilator, oedema-potentiating prostaglandins were released. However, it was likely that other vasodilators were also generated. 5. Antihistamines were poor inhibitors of oedema formation as were PAF antagonists, a 5-lipoxygenase inhibitor, a kallikrein inhibitor, a bradykinin antagonist and anti-C5a antibody. 6. Local oedema formation in the PCA was partially reduced by neutrophil depletion and colchicine suggesting that neutrophil-dependent mediators were involved. 7. Exudate fluid from anaphylactic reactions in the rabbit peritoneal cavity contained permeability-increasing activity when injected into rabbit skin. This activity is now being characterized. 8. A vasodilator prostaglandin appears to be released in the rabbit PCA reaction but none of the established permeability-increasing mediators appears to be involved. Thus, there may be novel inflammatory mediators generated in this reaction which may have relevance for human allergic skin diseases.

Anti-inflammatory effect of cyclosporin A on human skin mast cells

We have examined the effects of cyclosporin A (CsA) and cyclosporin H (CsH), which bind with different affinity to cyclophilin, to evaluate the role of this protein in the release of preformed (histamine) and de novo synthesized (prostaglandin D2[PGD2]) mediators of inflammatory reactions from human skin mast cells (HSMC). CsA (2.4-800 nM)-inhibited (5-60%) histamine release from HSMC challenged with anti-IgE. CsA exerted little, if any, inhibitory effect on histamine release from HSMC challenged with compound A23187 and substance P, whereas it completely suppressed A23187-induced histamine release from human basophils. Inhibition of histamine release from HSMC challenged with anti-IgE was extremely rapid and was not abolished by washing (three times) the cells before anti-IgE challenge. CsA (2.4-800 nM) markedly inhibited (25-70%) the de novo synthesis of PGD2 from HSMC challenged with anti-IgE. CsH, which has an extremely low affinity for cyclophilin, had no effect on skin mast-cell mediator release. These data suggest that CsA is a potent anti-inflammatory agent acting on HSMC, presumably by interacting with cyclophilin.

Inhibitory effects of formoterol and terbutaline on the development of late phase skin reactions

The capacity of the beta 2-agonist terbutaline and the longer-acting beta 2-agonist formoterol to suppress the development of late phase skin reactions to anti-human IgE was evaluated in 17 healthy volunteers. Anti-IgE injected intradermally per se induced an early weal and flare reaction, followed by a progressively increasing induration, the LCR, with a duration of greater than or equal to 24 hr. The LCR was inhibited by 40% when the weal was infiltrated with formoterol 250 ng 30 min after challenge (n = 9, P less than 0.01). The same anti-LCR effect was achieved by compensating for the shorter duration of action of terbutaline with repeated drug infiltration in 12.5 micrograms doses of the weal produced by anti-IgE up to 3 1/2 hr after challenge (n = 8). The data support the hypothesis that beta 2-agonists, both short- and long-acting, inhibit IgE-dependent LCRs by preferentially interacting with inflammatory events after the initial mast cell degranulation.

Profile of prostanoid release following antigen challenge in vivo in the skin of man

We have previously characterized the kinetics of prostaglandin D2 (PGD2) production at cutaneous sites of allergic inflammation employing a blister-chamber model. In this study, a more complete profile of prostaglandins released in vivo was obtained. PGD2 release, as measured by radioimmunoassay and by combined gas chromatography-mass spectrometry, was evident within 1 h after antigen challenge with maximal levels occurring 3-4 h post-challenge. The 11-ketoreductase metabolite of PGD2, 9 alpha, 11 beta-prostaglandin F2 was present in blister fluid from three of six patients at the time of maximal levels of PGD2. The stable non-enzymatic hydrolysis product of prostacyclin, 6-keto-prostaglandin F1 alpha, was significantly elevated in blister fluid from five of six patients following antigen challenge. In these subjects, the levels of 6 kappa-PGF1 alpha were highest in samples obtained 1 and 2 h after antigen challenge and remained significantly elevated until 5 h post-challenge. Levels of prostaglandin E2, prostaglandin F2 alpha and thromboxane B2 did not vary significantly. These studies suggest that following antigen challenge two fatty-acid cyclo-oxygenase products of arachidonic acid are released, PGD2 and prostacyclin. The 11-ketoreductase metabolism of PGD2 to 9 alpha, 11 beta-PGF2 could represent a mechanism by which the biological effects of PGD2 are prolonged in cutaneous tissue. The presence of 6 kappa-PGF1 alpha in the blister fluid suggests that significant prostacyclin release occurs as the result of antigen challenge and could represent a mechanism by which the prolonged microvascular response in cutaneous tissue may occur.

Increased tryptase levels in suction-blister fluid from patients with urticaria

The levels of tryptase in the suction-blister fluid from patients with chronic urticaria, urticaria pigmentosa, cholinergic urticaria, urticarial dermographism, prurigo of unknown origin, eczema, psoriasis, atopic dermatitis, and from healthy controls were studied. The blister fluid from controls contained up to 15 micrograms/l of tryptase, whereas that from patients with active urticaria contained greater than 50 micrograms/l. This study demonstrates that patients with urticaria have mast cells that readily release tryptase in both the lesional and non-lesional areas of skin.

Flare factors and atopic dermatitis: the role of allergy

Atopic dermatitis is a genetically determined eczematous skin disease strongly influenced by environmental conditions called flare factors. Allergic reactions are one such flare factor. These reactions include contact urticaria, allergic contact dermatitis, and late phase reactions. Contact urticaria could induce eczema by eliciting scratching. A late phase reaction may be involved in eczema produced by prolonged epicutaneous applications of antigens in individuals with immediate sensitivity to these antigens. Mechanisms of allergic contact dermatitis might also elicit dermatitis. Environmental allergens may include mold, dust, mite, pollens, foods, danders and bacteria.

Inhibition of anti-IgE induced skin response in normals by formoterol, a new beta 2-adrenoceptor agonist, and terbutaline. 2. Effect on the late phase reaction

Formoterol, a new beta 2-selective long-acting bronchodilator, was compared with terbutaline in terms of ability to inhibit dual phase skin reactions to anti-human IgE in volunteers. Anti-IgE induced an early wheal and flare reaction (WFR) followed by a progressively increasing induration, the late phase reaction (LCR), lasting greater than or equal to 24 h. Intradermal injection of formoterol 20 ng or terbutaline 500 ng 5 min before challenge gave equal inhibition of the WFR. The subsequent LCR was suppressed by formoterol (30%) for the whole 24 h period, while terbutaline only attenuated the first 4 h period. Increasing the dose range of both drugs 25-fold, caused a further analogous reduction of the WFR to anti-IgE. In this higher dose range formoterol (0.5 micrograms) antagonized the following 1-24 h LCR by 50%, while terbutaline (25 micrograms) only attenuated the LCR by an average of 20%, with higher effect in the first 6 h period. The anti-LCR capacity of formoterol was highly superior to that of terbutaline (P less than 0.001). The histamine-elicited wheal response was attenuated by both drugs, but they had no effect on the flare response, favouring an anti-permeability action of both compounds. The data support the concept that terbutaline, given locally in a single dose shortly before challenge, inhibits the mast cell mediator release reaction with limited consequences for the following LCR. In contrast to terbutaline, formoterol exerted a substantial anti-LCR action, probably by interfering with inflammatory mechanisms after the initial mast cell mediator release.

Interactions between histamine and prostanoids in IgE-dependent, late cutaneous reactions in man

The contribution of histamine and cyclooxygenase metabolites of arachidonic acid to the wheal-and-flare reaction (WFR) (0 to 30 minutes) and the late cutaneous reaction (LCR) (1 to 24 hours) evoked by intradermal injection of antihuman IgE was appreciated in a comprehensive study of human volunteers treated with H1 and H2 antihistamines, cyclooxygenase inhibitors, as well as the combination of both types of drugs. The findings reinforce the concept that histamine is the major, but not exclusive, mediator of the WFR. In contrast, histamine accounted for but a limited portion of the LCR, but 48 hours of pretreatment with three different cyclooxygenase inhibitors, acetylsalicylic acid, indomethacin, or diclofenac sodium, had but a minor influence on the WFR, whereas all drugs produced a distinct overall inhibition of the LCR. However, for indomethacin, the inhibition was preceded by a potentiation (at 1 to 2 hours), which was abolished by antihistamines, suggesting increased histamine release from skin mast cells after cyclooxygenase inhibition. Furthermore, there was synergism between indomethacin and antihistamines during the LCR, and the combination of diclofenac sodium with antihistamines produced additive inhibition. It is proposed that cyclooxygenase products, such as prostaglandins and thromboxanes, contribute to IgE-dependent skin reactions, both as modulators of mediator release and as vasoactive mediators.

Inflammatory mediator release on conjunctival provocation of allergic subjects with allergen

To evaluate the role of inflammatory mediators in the pathogenesis of the ocular allergic response, 23 subjects with positive histories of allergies to either cat dander or ragweed pollen and positive skin tests to the appropriate allergen extract were recruited and were subjected to conjunctival provocation. The tear duct of the left eye of each subject was blocked with a collagen plug while the right eye was left unplugged. In all cases, the eye was initially provoked with saline and subsequently with the appropriate allergen extract. Nonallergic subjects, or allergic subjects provoked with nonrelevant allergen, were used as control subjects. After each provocation, symptoms were recorded, and tears were collected with preweighed strips of filter paper (Schirmer strip). Each strip was placed into a tared tube containing fluid appropriate for the optimal preservation of the mediator to be measured. It was therefore possible to calculate the weight of tears collected and to express mediator levels per milliliter of tears. All allergic subjects demonstrated a positive symptomatic response to allergen challenge, whereas the control subjects remained asymptomatic. Blockage of the tear duct did not significantly alter the response. For allergic subjects, the levels of histamine, kinins, prostaglandin D2, albumin, and TAME-esterase activity were all significantly (p less than 0.005 in each case) greater after allergen challenge than after saline challenge. Furthermore, levels of each of these mediators after allergen challenge (expressed as increases above levels after saline provocation) were significantly greater for allergic subjects than for control subjects (p less than 0.005 in each case). Thus, the clinical response to conjunctival provocation with allergen is associated with increases in the levels of inflammatory mediators in tears.

Cutaneous late-phase response to allergen. Mediator release and inflammatory cell infiltration

To better define the inflammatory infiltrates and kinetics of mediator release during the cutaneous late-phase reaction (LPR), we examined skin biopsies at 8 h, and skin chamber cell counts and mediator release for 12 h after antigen challenge. Compared with the control sites, the antigen-stimulated biopsy sites contained 14 times as many basophils (P less than 0.01) and six times as many eosinophils (P less than 0.001) with one to two fold more mononuclear cells (P less than 0.03) and neutrophils (P less than or equal to 0.01). Similar changes were found in the skin chambers. Although there were neutrophils in the control chamber, they were only twice as numerous in the antigen challenged site (P less than 0.01). Eosinophils were 35-fold (P less than or equal to 0.03) more prevalent in the antigen chamber than the control chamber for hours 8-12 and basophils were noted starting in the eighth hour and were 20-fold (P less than or equal to 0.03) more concentrated in the antigen chamber during the next 4 h. The mononuclear cells were not significantly different between antigen and control blisters. With respect to inflammatory mediators, there was an initial peak of histamine (13.2 +/- 2.9 ng/ml) in the blister fluid at 1 h. The level then fell to approximately 2 ng/ml, followed by a secondary rise starting at the eighth hour and increasing to 9.8 +/- 2.8 ng/ml by the twelfth hour. This secondary increase in histamine correlated significantly (r = 0.81, P less than 0.05) with the observed influx of basophils. PGD2 in the blister fluid rose to 371+/-25 pg/ml during the first 4 h and then slowly decreased to half this level during the last 4 h. Thus, the cutaneous LPR has been shown to manifest a secondary increase in histamine levels and a markedly specific increase in eosinophils and basophils with mediator release apparently being derived from the latter cells.