Effect of H1-receptor blockade on late cutaneous reactions to antigen: a double-blind, controlled study

Effect of tecastemizole on pulmonary and cutaneous allergic inflammatory responses

BACKGROUND

Tecastemizole, a major metabolite of astemizole, is a potent and selective H1 receptor antagonist. Evidence suggests that this and certain other H1 receptor antagonists may possess anti-inflammatory effects that are, in some cases, independent of H1 receptor antagonism. Objective The aim of this study was to investigate the anti-inflammatory effects of tectastemizole in models of allergic inflammation.

METHODS

Effects of tecastemizole were assessed in a murine model of allergic lung inflammation, in passive cutaneous anaphylaxis (PCA) responses in guinea-pig skin and in in vitro assays measuring endothelial adhesion molecule expression and leucocyte-endothelial adhesion.

RESULTS

Tecastemizole inhibited antigen-induced eosinophil recruitment to the lungs of allergic mice in a dose-dependent manner. Furthermore, combination of a sub-effective dose of tecastemizole, combined with a sub-effective dose of dexamethasone inhibited eosinophil accumulation in this model. Plasma extravasation in PCA reactions was inhibited by tecastemizole, although by a mechanism that would appear to be H1 receptor-dependent. Cytokine-induced endothelial intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression, as well as mononuclear cell adhesion to human umbilical vein endothelial cells was inhibited by tecastemazole in a manner independent of H1 receptor antagonism.

CONCLUSION

These data suggest that tecastemizole may have H1 receptor-independent effects in inhibiting late-phase inflammatory responses, while acute responses appear to be inhibited in a H1 receptor-dependent manner. Furthermore, our data suggest an important potential steroid-sparing role for such drugs in the treatment of allergic inflammatory conditions.

Suppression of the early and late cutaneous allergic responses using fexofenadine and montelukast

BACKGROUND

The relative contribution of histamine and the cysteinyl leukotrienes to the early and late cutaneous allergic responses (ECAR and LCAR) can be studied using antagonists of these mediators.

OBJECTIVE

To determine the relative suppression of the ECARs and LCARs using standard doses of an H1-receptor antagonist, a cysteinyl leukotriene1-receptor antagonist, and the two antagonists administered concurrently.

METHODS

We carried out a prospective, randomized, double-blind, placebo-controlled, four-way crossover study in 12 highly allergic participants. Intradermal tests with standardized allergen, and with histamine phosphate, LTD4, and saline controls were performed on 5 different test days as follows: pretreatment baseline and at steady state immediately after the seventh and last dose of a 1-week course of treatment with once-daily fexofenadine, 120 mg; montelukast, 10 mg; fexofenadine and montelukast administered concurrently; or placebo. On each test day, the skin test results were read at intervals from 0.25 to 24 hours after the intradermal injections were performed.

RESULTS

After allergen injection, compared with baseline, all treatment regimens significantly decreased the ECAR and LCAR. After allergen injection, compared with placebo, fexofenadine significantly decreased the ECAR and the LCAR from 0.25 to 2 hours and at 8 hours. Montelukast did not significantly decrease the ECAR or LCAR. Fexofenadine and montelukast administered concurrently were not more effective than fexofenadine alone at any time. In the control skin tests, compared with placebo, fexofenadine, but not montelukast, significantly decreased the histamine-induced response, and montelukast, but not fexofenadine, significantly decreased the LTD4-induced response.

CONCLUSIONS

Fexofenadine and montelukast administered concurrently were not significantly more effective than fexofenadine alone in decreasing the ECAR and LCAR. Montelukast does not need to be discontinued before allergen skin testing. Further studies of the effect of concurrent treatment with higher doses of a histamine antagonist and a leukotriene modifier on the allergic response in the skin are needed.

Immunohistochemical investigation of the cellular infiltrates at the sites of allergoid-induced late-phase cutaneous reactions associated with pollen allergen-specific immunotherapy

BACKGROUND

Reduction in the size of the allergen-induced late-phase reaction (LPR) is seen as a consequence of successful allergen specific immunotherapy.

OBJECTIVE

It was the aim of this study to characterize the cellular infiltrate at the sites of cutaneous LPR that may occur following injection of a depot pollen allergoid (Allergovit(R)) during immunotherapy and thereby determine the immunological nature of the response.

METHODS

Punch biopsies were taken 24 h after subcutaneous injection of a depot pollen allergoid from eight patients that showed LPR and a further five patients that did not. Additional biopsies taken 24 h after injection of allergoid-free depot in the same patients served as controls. Immunoenzymatic labelling of the cryostat sections with different antibodies was performed with the APAAP technique. Results were expressed as cells/field (400 x magnification).

RESULTS

Similar dermal cellular infiltrations were seen following depot allergoid injections in patients both with and without LPR. Patients with LPR showed statistically significant increases in total cells, CD4+ cells, CD11c+ cells, CD45RO+ cells, CD45RB+ cells and activated eosinophils at the reactions sites as compared with control sites. In patients without LPR CD11c+ cells, HLA-DR+ cells and CD45RA+ T cells increased significantly. CD8+, CD1a+, NP57+, CD23+ and CD25+ cells did not differ significantly in either group.

CONCLUSION

These results indicate that activation of T cells, monocytes/macrophages and eosinophils at the sites of LPR following injection of depot allergoid are comparable with those following injection of allergen. Even in the absence of a cutaneous LPR, subsets of T cells and monocytes/macrophages increased. These cell activations may reflect events associated with the mechanisms of allergoid-based specific immunotherapy, and suggest that at least part of the late-phase reaction may be independent of IgE.

Cellular inflammatory responses during immediate, developing, and established late-phase allergic cutaneous reactions: effects of cetirizine

BACKGROUND

In some previous studies, the antihistamine cetirizine has inhibited both developing (at 6 hours) and established (at 24 hours) gross late-phase skin reactions (LPR) to pollen antigens, possibly relevant to clinical drug effects. However, the effects of cetirizine at the histologic level require further definition.

OBJECTIVE

To characterize cetirizine effects on gross and histologic inflammatory events from 20 minutes to 24 hours after intradermal antigen challenge in sensitive patients.

METHODS

Gross and histologic responses to intradermal pollen antigen, codeine, histamine, and buffer diluent were assessed during randomized 7-day treatments with cetirizine and placebo. Accumulated neutrophils, eosinophils, activated (EG2+) eosinophils, and T lymphocytes were quantitated. The degrees of extracellular deposition of lactoferrin from neutrophils and eosinophilic cationic protein (ECP) from eosinophils were also assessed.

RESULTS

During placebo treatment, wheal-and-flare responses were significantly greater to antigen at 20 minutes (p < 0.01) and induration at 6 hours (p < 0.01) at antigen challenge sites than at buffer diluent sites. During cetirizine treatment, these wheal-and-flare responses to antigen were inhibited significantly (p < 0.01) but gross LPRs were not affected. During placebo treatment, significantly more cells per high-power field were found in antigen sites than in buffer sites of neutrophils at 20 minutes (p < 0.01) and 24 hours; than in eosinophils at 20 minutes, 6 hours, and 24 hours (p < 0.01 for each); than in EG2+ cells at 20 minutes (p = 0.004), 6 hours (p = 0.001), and 24 hours (p = 0.02); and at T lymphocyte sites at 24 hours (p = 0.001). Extracellular deposition of lactoferrin and ECP was significantly greater at antigen sites than at buffer sites at 6 and 24 hours. Cetirizine treatment had no significant effect on these responses.

CONCLUSION

Neutrophils, eosinophils, and T lymphocytes were persistently more common at antigen sites than at buffer sites through 24 hours. Many of these neutrophils and eosinophils were activated, releasing more lactoferrin and ECP into the extracellular dermis for at least 24 hours after antigen challenge. Cetirizine inhibited gross immediate responses to antigen, but not the gross LPR nor the cellular inflammatory responses seen in such LPR sites.

Microvascular mechanisms of histamine-induced potentiation of leukocyte adhesion evoked by chemoattractants

1. Intravital microscopy of the rat mesentery was used to examine interactions between histamine and the chemoattractant leukotriene B4 (LTB4) with regard to leukocyte adhesion in postcapillary venules. 2. Topical administration of histamine caused a four fold potentiation of LTB4-induced leukocyte adhesion. 3. Histamine significantly increased the rolling leukocyte flux by 25%, and this effect of histamine on rolling was strictly blood flow-dependent, i.e. we found significant positive correlations between both blood flow and total leukocyte flux and between total and rolling leukocyte flux, while no changes in leukocyte rolling fraction or rolling velocity were observed. Furthermore, histamine caused a clear-cut increase in venular plasma protein leakage. 4. The platelet-activating factor (PAF) receptor antagonist WEB 2086, which effectively inhibited adhesion of leukocytes evoked by exogenous PAF, did not reduce the potentiating effect of histamine on LTB4-induced leukocyte adhesion. 5. The vasodilator acetylcholine (ACh) caused a moderate enhancement of LTB4 induced leukocyte adhesion in proportion to its blood flow-dependent 40% increase in rolling leukocyte flux. In contrast to histamine, ACh did not provoke vascular leakage of plasma proteins. 6. Taken together, our findings suggest that histamine plays an important pro-inflammatory role in tissues where leukocyte rolling is already present, by potentiating chemoattractant-induced firm leukocyte adhesion through a combination of microcirculatory changes such as increased rolling leukocyte flux and vascular permeability.

Effects of loratadine on anti-IgE-induced inflammation, histamine release, and leukocyte recruitment in skin of atopics

The aim of this study was to assess the ability of the H1-receptor antagonist loratadine to modify anti-IgE-induced cutaneous wheal-and-flare and late-phase reactions (WFR and LPR), as well as histamine release and leukocyte accumulation in skin chambers. For this purpose, 10 atopics with allergic rhinitis were entered into a double-blind crossover study in which they received either placebo or loratadine (20 mg/day orally) for 8 days separated by a 7-day washout period. Blisters were induced on both forearms on day 7 of each treatment period, and were unroofed on day 8 and covered with plastic skin chambers. Chamber fluids were collected during 7 h after 1-h incubation with anti-IgE or control IgG. Intradermal challenge with histamine and anti-IgE was performed at the same occasion. As compared to placebo treatment, loratadine inhibited the immediate WFRs to anti-IgE by 35% (wheal) and 65% (flare), respectively (P < 0.01), and corresponding reactions to histamine challenge by 50% and 70% (P < 0.001), respectively. Moreover, the initial phase (0-2 h) of the LPR induced by anti-IgE was attenuated by up to approximately 60% (P < 0.001) during loratadine treatment. Thereafter, no inhibition of the LPR was observed. The magnitude and time course of histamine release into skin chambers was virtually the same after loratadine and placebo treatment, with a peak during 0-1 h and a progressive decline during the following 2 h. Accumulation of alpha 2-macroglobulin, reflecting extravasation of large plasma proteins, also peaked during the first hour and was unaffected by loratadine during the 8-h observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Cutaneous IgE-mediated inflammatory lesion size is inhibited by an H1 antagonist (terfenadine) while mediator release is unaffected in vivo and in vitro

We are interested in understanding the pathogenesis of the cutaneous IgE-mediated late phase reaction. A double-blind, placebo-controlled, randomized cross-over study with 10 subjects of the effect of the non-sedating antihistamine, terfenadine (Selddane), on the cutaneous reaction to antigen (ragweed or mixed grass) administered intradermally and over denuded blister bases was performed. The activity of terfenadine on anti-IgE-induced mediator release from the skin mast cell, lung mast cell and basophil was also examined in vitro. Terfenadine significantly inhibited the size of the cutaneous reaction at every hour between hours 1 and 9 (hr 9, control 2250 +/- 500 mm2 vs drug 1250 +/- 250 mm2, P < 0.01, n = 10) and showed some inhibitory effect at hours 10-12. While terfenadine blocks histamine release after nasal antigen challenge the release of mediators at skin blister sites was unaffected. The infiltration of leucocytes into the blister supernatant was unaffected by terfenadine although previous studies have shown significant inhibition with another antihistamine, cetirizine. In vitro, terfenadine, like other antihistamines, was found to have inhibitory activity on anti-IgE-induced mediator release at concentrations of 10(-4)-10(-5) M in lung and skin mast cells and basophils. We conclude that the effects of the newer antihistamines on cellular movement into the skin may be diverse, that terfenadine may show organ specificity in vivo and that terfenadine significantly decreases both the early and late gross inflammatory response of the skin to antigen. We cannot, as yet, explain the mechanism(s) by which this occurs.