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Background: The CXC chemokine receptor 4 (CXCR4) is predominantly expressed on inactivated naive T lymphocytes, B lymphocytes, dendritic cells, and endothelial cells. CXC chemokine stromal cell-derived factor 1alpha (SDF-1alpha) is the only known ligand for CXCR4. To date, the CXCR4 expression and function of SDF-1alpha in basophils are unknown., Objective: The purpose of this study was to investigate the expression of CXCR4 and functions of SDF-1alpha in basophils and to characterize the role of the CXCR4-SDF-1alpha receptor ligand pair in the allergic inflammation., Methods: Basophil purification, flow cytometry, real-time quantitative RT-PCR assay, Northern blotting, intracellular free Ca(2+) change, chemotaxis assay, and histamine release assay were used., Results: CXCR4 is abundantly expressed on peripheral blood resting basophils (91%). Likewise, CXCR4 messenger (m)RNA is expressed in resting basophils (3.2 x 10(3) copies per 2 x 10(2) cells). The existence of CXCR4 mRNA was also confirmed in basophils by means of Northern blot analysis. SDF-1alpha induces an increase in intracellular free Ca(2+) in basophils. SDF-1alpha activates basophils to chemotaxis (chemotactic index = 3.8) and histamine release (36% of total content) through CXCR4 on the cells. The chemokines SDF-1alpha, eotaxin, RANTES, monocyte chemoattractant protein (MCP) 1, and macrophage inflammatory protein (MIP) 1alpha have been demonstrated at different potencies in induction of chemotaxis (eotaxin > SDF-1alpha > RANTES congruent with MCP-1 >> MIP-1alpha) and histamine release (MCP-1 congruent with SDF-1alpha > eotaxin > RANTES > MIP-1alpha). The optimal concentration seen for SDF-1alpha effects (chemotaxis and histamine release) on basophils was 100 ng/mL., Conclusion: These results indicate that the CXCR4-SDF-1alpha receptor ligand pair may be important for the recruitment and activation of the basophils, which is a characteristic effector cell of the allergic inflammation.

Background: Antihistamines (H1-receptor antagonists) act by competitive antagonism of histamine at H1-receptors. In addition, high concentrations of some antihistamines inhibit allergen-induced histamine release from mast cells in vitro., Objective: The purpose of this study was to determine the effect of intranasal azelastine or systemic cetirizine (both potent antihistamines) on the allergen-induced release of mast-cell mediators from the human nasal mucosa in vivo., Methods: Patients allergic to birch pollen (n = 11) and control subjects not allergic to birch pollen (n = 5) were included in a randomized, double-blind, placebo-controlled, 3-way crossover study outside the pollen season. Each subject was treated with azelastine nasal spray 0.14 mg per nostril twice daily, cetirizine tablets 10 mg every day, or placebo for 1 week using a double-dummy design. At the end of each treatment period, nasal allergen challenges were performed, and the number of sneezes were counted. In addition, nasal lavage fluid was collected, and the levels of mast-cell mediators (histamine and tryptase) were measured., Results: The allergen challenge of patients allergic to pollen produced sneezing and a significant increase in the levels of histamine and tryptase. The challenge of subjects not allergic to pollen produced no such response. Azelastine and cetirizine significantly reduced allergen-induced sneezing and the associated increase in histamine and tryptase levels. No significant differences were found between the azelastine and cetirizine treatments., Conclusion: Pretreatment with azelastine or cetirizine inhibits the allergen-induced release of mast-cell mediators from the human nasal mucosa. Our results are consistent with the hypothesis that both antihistamines reduce mediator release from nasal mucosa mast cells in vivo. However, further studies are necessary to test this hypothesis.

Background: Intradermal injection of platelet-activating factor (PAF) causes wheal and flare reactions, which are inhibited by antihistamines. However, PAF does not release histamine from human dispersed skin mast cells in vitro. The purpose of this study was to investigate the extent and possible mechanisms of PAF-induced histamine release in human skin in vivo with the use of dermal microdialysis., Methods: Hollow dialysis fibers were inserted into the upper dermis in forearm skin and each fiber was perfused with Krebs-Ringer bicarbonate solution at a rate of 3.0 microliters/min. PAF (4.5 to 36 mumol/L), lyso-PAF (36 mumol/L), vehicle (negative control), and codeine 750 or 250 mumol/L (positive control) were injected intradermally above separate fibers. Dialysate was collected in 2-minute fractions for 20 minutes and histamine analyzed spectrofluorometrically., Results: PAF, but not lyso-PAF, caused statistically significant dose-related histamine release and wheal and flare reactions. Intradermal mepivacaine administration significantly abrogated flare reactions by PAF and codeine and inhibited histamine release and wheal reactions by PAF but not by codeine. Long-term topical capsaicin administration inhibited histamine release and wheal reactions by PAF but not by codeine. It inhibited flare reactions induced by both compounds. PAF did not release histamine from blood basophils., Conclusions: These data suggest that PAF induced histamine release from mast cells in intact human skin indirectly via neurogenic activation. Further, on the intradermal injection of PAF histamine release and the skin responses, the wheal and the flare, are differentially regulated by neurogenic components.

Background: The chemokines monocyte chemoattractant factor-1, RANTES, and macrophage inflammatory protein-1 alpha release histamine from human basophils, as well as rat and mouse mast cells. The purpose of this investigation was to determine whether these chemokines release histamine from human skin mast cells in situ., Methods: A microdialysis technique was used to measure histamine release in skin. First, the model was validated by using anti-IgE, codeine, and stem cell factor (SCF); then the histamine-releasing effects of the chemokines were investigated. A total of 47 skin specimens from 41 donors were investigated. Hollow microdialysis fibers were inserted intradermally, and each fiber was slowly perfused (3 microliters/min). Anti-IgE, codeine, SCF, or chemokines were injected intradermally above individual fibers, and dialysate was collected at 2-minute intervals for 20 minutes. Each series of investigations comprised five to eight single experiments., Results: Anti-IgE (4 to 4000 U/ml), codeine (0.001 to 1 mg/ml), and SCF (5.4 x (10(-11) to 10(-8) mol/L)) released histamine in a dose-dependent manner; maximum histamine release was 97.4, 116.3, and 9.5 pmol/20 min, respectively. Monocyte chemoattractant factor-1, RANTES, and macrophage inflammatory protein-1 alpha in concentrations of 10(-10) to 10(-6) mol/L did not release histamine; histamine release by 10(-6) mol/L chemokine was less than 0.2 pmol/20 min. None of the chemokines modulated anti-IgE-induced histamine release. In contrast, SCF significantly potentiated anti-IgE-induced histamine release by 33%. All chemokines, but not SCF, released histamine from human basophils., Conclusion: We conclude that the chemokines monocyte chemoattractant factor-1, RANTES, and macrophage inflammatory protein-1 alpha do not release histamine from human skin mast cells.

Background: The purposes of the study were to characterize allergen-induced histamine release in intact human skin in vivo by using a novel microdialysis technique and to study covariates influencing histamine releasability., Methods: Hollow microdialysis fibers were inserted into the upper dermis in 15 timothy-sensitivity subjects. Up to 12 fibers were inserted in each subject. Each fiber was perfused with Krebs-Ringer's solution at a rate of 3.0 microliters/min. Three to four serial dilutions of allergen were applied to the skin by intracutaneous injections or skin prick test above individual fibers. Samples were collected in two 2-minute fractions before skin challenge and in 10 consecutive samples for 20 minutes after skin challenge. Histamine was assayed spectrofluorometrically., Results: A significant dose-response relationship for histamine release was demonstrated with intracutaneous tests and skin prick tests. The time to reach peak histamine release after an intracutaneous test was 4 to 8 minutes, compared with 12 to 14 minutes for a skin prick test. Histamine release correlated significantly with wheal size. Intrasubject coefficient of variation on histamine release was about 20%. A substantial intersubject variation in histamine releasability was observed. Seventy to seventy-five percent of the variation could be accounted for by a combination of gender, total and allergen-specific IgE, and an in vitro basophil histamine release test., Conclusions: Using a skin microdialysis technique, we have described in detail histamine release in intact human skin by allergen. The microdialysis method proved to be a reproducible technique for monitoring histamine release in allergic skin reactions and for studying histamine releasability of skin mast cells in vivo.

Background: The purpose of this study was to introduce a microdialysis technique, which makes it possible to measure the release of small inflammatory mediators into the extracellular water space in intact human skin in vivo. Using this technique, we have studied the histamine releasing properties of substance P, a putative skin mast cell releasing agent., Methods: Small hollow fibers were inserted into the upper dermis of nine healthy subjects. Each fiber was perfused with Kreb's Ringer bicarbonate buffer at a rate of 3.0 microliters/min. After establishment of a baseline, each fiber was challenged intracutaneously with substance P (0 to 4 mumol/L). Samples were collected at 2-minute intervals for 18 minutes. Histamine was measured by a fluorometric method, which correlated with an enzyme immunoassay (r = 0.96)., Results: Baseline dialysate histamine concentration was 1.7 +/- 0.3 ng/ml. Peak histamine release after injection of vehicle, 0.5, 1, 2, and 4 mumol/L substance P was 0.0, 1.0, 6.0, 44.5, and 88.5 ng/ml, respectively (p = 0.00002). Statistically significant histamine release was demonstrated with 1.0 mumol/L substance P and greater. Most peak values were seen 2 to 4 minutes after injection. The histamine elimination showed a monoexponential decline; dialysate histamine half-life was 3.81 +/- 0.28 minutes., Conclusions: This study showed that substance P releases histamine in a dose-dependent manner from intact human skin in normal subjects. We suggest that microdialysis may be a promising technique for the evaluation of mediator levels in intact human skin after intradermal injection of an inflammatory or allergenic stimulus.

The determination of histamine in nasal secretions and nasal lavage fluid may be of importance to monitor activation of histamine containing cells in the nasal cavity. However, such studies have been besieged by controversy, specifically to findings of changes in histamine levels in relation to allergenic stimulation. This controversy may be due to the specificity and accuracy of the various methods used to determine histamine in the nasal fluid. We have therefore applied and compared three new methods to determine histamine in nasal lavage fluids obtained before and after allergen challenge in normal subjects and patients with allergic rhinitis. We used a fluorometric glass fiber-based histamine method (FHR) and two RIAs, I and II. The FHR (detection limit, 7.0 nmol) and the RIA II (detection limit, 0.2 nmol) are specific for histamine itself, whereas the RIA I (detection limit, 18.0 nmol) measures mainly methylhistamine and cross-reacts to some extent with histamine. The histamine levels in the nasal lavage fluids from the nasal challenges demonstrated histamine values between 100 and 2000 nmol/L of histamine with significantly higher levels in the postallergen challenges for the allergic subjects as compared to the normal control subjects. The FHR correlated well with the RIA I and RIA II methods with correlation coefficients of 0.77 to 0.88 (p less than 0.001), respectively. However, the RIA I (methylhistamine antibody) always demonstrated absolute histamine values 5% to 20% of values measured by the RIA II (at the level of cross-reactivity to histamine).(ABSTRACT TRUNCATED AT 250 WORDS)