The pattern and kinetics in human skin of erythema and mediators during the acute and late-phase response (LPR)

Calcitonin gene-related peptide and vascular endothelial growth factor are expressed in lesional but not uninvolved skin in chronic spontaneous urticaria

BACKGROUND

The mechanisms for producing weals in chronic spontaneous (idiopathic) urticaria (CSU) are incompletely understood. Leucocyte infiltration with vascular leakage and expression of the potent vasoactive agents' calcitonin gene-related peptide (CGRP) and vascular endothelial growth factor (VEGF) are features of late-phase allergic skin reactions, previously proposed as a model of CSU.

OBJECTIVE

To measure CGRP and VEGF expression in lesional and non-lesional skin from CSU patients and to compare results with a control group.

METHODS

Eight paired biopsies (one from 4-8 h spontaneous weals and one from uninvolved skin) were taken from eight patients with CSU and nine control subjects and studied by immunohistochemistry and confocal microscopy.

RESULTS

Lesional skin in CSU contained significantly more CGRP+ and VEGF+ cells than non-lesional skin. No significant differences were observed in CGRP and VEGF expression between non-lesional skin and controls. In lesional skin, VEGF and CGRP co-localised to UEA-1+ blood vessels. CGRP was also expressed by neutrophils and eosinophils and to a lesser extent by CD90(+) fibroblasts, mast cells, CD3(+) and CD68(+) cells. CGRP and VEGF expression was not related to the duration of disease.

CONCLUSION AND CLINICAL RELEVANCE

Increased expression of CGRP and VEGF in lesional, but not uninvolved, skin indicates that these potent vasoactive agents may play a role in wealing and tissue oedema in CSU so representing novel targets in therapy.

A double-blind, placebo-controlled trial of montelukast in adult atopic eczema

BACKGROUND

Montelukast is an antagonist of cys-leukotriene receptors used mainly in the treatment of asthma- and seasonal-allergic rhinitis. Initial reports concerning the use of montelukast in atopic dermatitis (AD) have been encouraging, although not consistent.

OBJECTIVES

We have undertaken a randomized, double-blind, parallel-group, placebo-controlled trial to investigate further the efficacy of montelukast in the treatment of atopic eczema.

METHODS

Following a screening visit, subjects received placebo treatment for 2 weeks in a single-blind phase, followed after visit 2 by an 8-week, double-blind period of treatment with montelukast 10 mg daily or placebo. Subjects were patients aged 16-60 years under our care for treatment of AD of moderate severity, defined by a six-area, six-sign atopic dermatitis (SASSAD) score in the range 12-50. Response to treatment was assessed by investigators and by subjects using a seven-point scale, with response defined as marked improvement or better. In addition, the SASSAD score was used to monitor the severity of clinical signs. The proportion of skin involved was estimated and visual analogue scales were used to record the severity of pruritus and sleep disturbance. Topical corticosteroid usage was recorded using a five-point scale. Adverse events were recorded.

RESULTS

Sixty subjects were recruited and 54 completed the study. The treatment groups were well matched for disease severity at baseline (SASSAD scores were 25 and 29 in the montelukast and placebo groups, respectively). There were no significant differences between the treatment groups in any of the parameters used to assess treatment response. The improvement in mean SASSAD score from baseline (visit 2) to the end of treatment was marginally superior in the placebo group, 1.41 points on montelukast vs. 1.76 on placebo, a difference of 0.35 (95% confidence interval -6.1 to 6.8). Adverse events were generally of a mild nature except for a brief septicaemic illness in one subject receiving montelukast.

CONCLUSIONS

The data do not support previous reports of efficacy of montelukast in treatment of AD.

Pharmacotherapy of diseases mediated by 5-lipoxygenase pathway eicosanoids

Inflammatory eicosanoids generated by the 5-lipoxygenase (5-LO) pathway of arachidonic acid metabolism are now known to have at least 6 receptors: OXE, which recognizes 5-HETE and 5-oxo-ETE; a putative receptor recognizing a potent 5-oxo-ETE metabolite, FOG(7); the LTB(4) receptors, BLT1 and BLT2; the cysteinyl leukotriene receptors, CysLT(1) and CysLT(2), which recognize leukotrienes LTC(4), LTD(4), LTE(4) and LTF(4). The 5-LO pathway is activated in many diseases and invokes inflammatory responses not affected by glucocorticoids, but therapy with selective BLT1 or CysLT(1) antagonists in asthma has met with variable success. Studies show that 5-LO pathway eicosanoids are not primary mediators in all cases of asthma, but may be especially important in severe persistent asthma, aspirin- and exercise-induced asthma, allergic rhinitis, COPD, idiopathic pulmonary fibrosis, atherosclerosis, atopic dermatitis, acne and ischemia-related organ injury. These disorders appear to involve multiple 5-LO pathway eicosanoids and receptor subtypes, suggesting that inhibition of the pathway at the level of 5-LO may be necessary for maximal efficacy.

Inflammation in allergic asthma: initiating events, immunological response and risk factors

Allergic asthma affects 155 million people worldwide. Currently, it is a disease that can be controlled by diverse therapeutic approaches but that cannot be cured. This means that asthma is one of the most expensive diseases for healthcare systems in developed countries. Efficient prevention strategies are therefore greatly needed to reduce both individual morbidity and national economic burdens. This requires a detailed knowledge of the immunological and physiological mechanisms involved in asthma. This review synthesizes current understanding about the immunobiology of IgE-mediated asthma. It discusses the initiating events, the main immunological and inflammatory processes, and addresses the importance of risk factors in the development and maintenance of allergic diseases. Finally, it integrates these concepts in a theoretical causal model for atopic asthma.

Intravenous anti-IL-5 monoclonal antibody reduces eosinophils and tenascin deposition in allergen-challenged human atopic skin

Anti-IL-5 monoclonal antibody (mepolizumab) reduces baseline bronchial mucosal eosinophils and deposition of extracellular matrix proteins in the reticular basement membrane in mild asthma. Here we report the effect of anti-IL-5, in the same patients, on allergen-induced eosinophil accumulation, tenascin deposition (as a marker of repair and remodelling) and the magnitude of the late-phase allergic cutaneous reaction. Skin biopsies were performed in 24 atopic subjects at allergen- and diluent-injected sites before 6 and 48 h after, three infusions of a humanized, monoclonal antibody against IL-5 (mepolizumab) using a randomized double-blind, placebo-controlled design. Anti-IL-5 significantly inhibited eosinophil infiltration in 6 h and 48 h skin biopsies as well as the numbers of tenascin immunoreactive cells at 48 h. In contrast, anti-IL-5 had no significant effect on the size of the 6 or 48 h late-phase cutaneous allergic reaction. This study (a) suggests that eosinophils are unlikely to cause the redness, swelling, and induration characteristic of the peak (6 h) late-phase cutaneous allergic reaction and (b) shows that decreases in tenascin positive cells at 48 h correlates with reduction of eosinophils, so providing further evidence of involvement in remodelling processes associated with allergic inflammation.

Late-phase reactions to intradermal testing with Dermatophagoides farinae in healthy dogs and dogs with house dust mite-induced atopic dermatitis

OBJECTIVE

To determine the prevalence of late-phase reactions to intradermal testing with Dermatophagoides farinae in healthy dogs and dogs with atopic dermatitis and an immediate reaction to D farinae.

ANIMALS

6 healthy dogs and 20 dogs with atopic dermatitis and immediate reactions to D farinae.

PROCEDURE

ntradermal tests were performed with D farinae at 1:1,000 wt/vol and 1:50,000 wt/vol concentrations, and skin reactivity was evaluated after 0.25, 6, and 24 hours. Serum D farinae-specific IgE antibodies were assayed. Extent of lesions (atopy index) and pruritus (visual analogue scale) were evaluated in dogs with atopic dermatitis.

RESULTS

Late-phase reactions were observed in healthy dogs at 6 hours (n = 2 dogs) and 24 hours (1) with the 1:1,000 wt/vol concentration, and at 6 hours (1) and 24 hours (1) with the 1:50,000 wt/vol concentration of allergen. Late-phase reactions in healthy dogs were only observed in dogs with an immediate reaction to D farinae. Late-phase reactions were observed in 11 of 20 dogs with atopic dermatitis at 6 and 24 hours with the 1:1,000 wt/vol concentration and in 10 of 20 at 6 and 24 hours with the 1:50,000 wt/vol concentration of allergen. There was no difference in mean atopy index, mean visual analogue scale of pruritus, or mean serum D farinae-specific IgE concentration of dogs with a late-phase reaction, compared to dogs without a late-phase reaction.

CONCLUSIONS AND CLINICAL RELEVANCE

Late-phase reactions may be observed after an immediate reaction to intradermal skin testing in healthy and allergic dogs but are more commonly observed in dogs with atopic dermatitis.

The ACVD task force on canine atopic dermatitis (VII): mediators of cutaneous inflammation

Controversy still exists on the role of various inflammatory mediators in the pathogenesis of canine atopic dermatitis. The objective of this article is to review the most recent information available on the inflammatory mediators that have been implicated in the pathogenesis of this disease. Studies on the role of histamine, serotonin, leukotrienes and various cytokines are presented in a comparative manner reviewing the experimental evidence for a role in the pathogenesis and the arguments against it.

Update on the role of leukotrienes in the pathogenesis of atopy: a comparative review

The pathogenesis of atopic disease (AD) is controversial in humans and dogs. In humans, leukotrienes (LT) are thought to play an important role in this disease and LT inhibitors are commonly used as treatment for AD. Leukotrienes are a heterogeneous group of biologically active compounds that mediate many aspects of inflammatory and allergic reactions. This paper will review the role of LT in atopic disease in a comparative manner. Leukotriene inhibitors and their therapeutic use in the management of atopic disease in humans and dogs are discussed.

Sulphido-leukotriene production from peripheral leukocytes and skin in clinically normal dogs and house dust mite positive atopic dogs

Pathogenesis of canine atopy has not been completely elucidated. In humans, sulphido-leukotrienes (s-LT) play a role in atopy, and increased production of s-LT occurs in the skin and peripheral leukocytes after allergen challenge. The study population included 16 clinically normal and 13 atopic dogs. All atopic dogs had in common a positive reaction (4+) to the intradermal injection of house dust mite (allergen of reference). Blood samples and skin biopsies were collected. Sulphido-LT synthesis by peripheral leukocytes after stimulation was measured, and no statistically significant difference was found between clinically normal and atopic dogs. Sulphido-LT concentrations in skin samples from stimulated and unstimulated sites were measured, and no statistically significant difference was detected between clinically normal and atopic dogs or between lesional and nonlesional skin within the atopic group. Clinical signs of atopic dogs were graded by owners and no correlation was found between their severity and cutaneous concentrations of s-LT. In this study there was no increase in s-LT synthesis in atopic dogs.

Chemical mediators in atopic dermatitis: involvement of leukotriene B4 released by a type I allergic reaction in the pathogenesis of atopic dermatitis

BACKGROUND

The mediators produced from a type I allergic reaction have not yet been able to explain the pathogenesis of atopic dermatitis (AD).

OBJECTIVE

The purpose of this study was to elucidate the involvement of leukotriene (LT) B4 produced from a type I allergic reaction in the pathogenesis of AD.

METHOD

The release of LTB4 was measured both in vitro, in passively sensitized and antigen-challenged human skin slices, as well as in vivo, in skin chambers on patients with AD.

RESULTS

LTB4 was released from in vitro human skin by stimulation of the antigen (54.9 +/- 14.6 pg/g wet weight of skin by antigen challenge and 28.0 +/- 11.1 pg/g in control skin, P <.002). Antigen-specific release of LTB4 and histamine was also observed in vivo in nonlesional skin from the patients with AD by using the skin chamber technique.

CONCLUSION

LTB4 release during type I allergic reaction in human skin has been determined in vitro. The released LTB4 possibly contributes to cellular response at the acute inflammatory lesion of AD.

Allergen-induced histamine release in intact human skin in vivo assessed by skin microdialysis technique: characterization of factors influencing histamine releasability

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.

Chemokines in seasonal allergic rhinitis

Monocyte chemotactic and activating factor/monocyte chemoattractant protein-1 (MCAF/MCP-1), RANTES, and macrophage inflammatory protein (MIP)-1 alpha are chemokines known to activate basophils (MCAF/RANTES) and eosinophils (RANTES/MIP-1 alpha). IL-8 inhibits MCAF-induced histamine release from basophils. We questioned whether a relationship exists between the levels of these chemokines and various inflammatory mediators released from mast cells, eosinophils, and basophils as assessed in nasal secretions obtained from patients during the allergy season and out of season. Samples were assessed for MCAF/MCP-1, RANTES, MIP-1 alpha, IL-8, histamine, tryptase and eosinophil cationic protein (ECP) in three subject groups: subjects with allergic rhinitis (n = 18), atopic subjects without rhinitis (n = 9), and healthy individuals (n = 6). Statistically significant differences were apparent only in the subjects with symptoms as follows. MCAF/MCP-1 increased during the season from 336 +/- 47 pg/ml to 829 +/- 137 pg/ml (p < 0.001), whereas IL-8 decreased from a baseline of 1932 +/- 335 pg/ml to 1070 +/- 202 pg/ml (p < 0.028). The ratio of IL-8 to MCAF/MCP-1 decreased during the symptomatic season from the baseline of 6.66 +/- 1.06 seen during winter to 1.3 +/- 0.22 during ragweed season (p < 0.001). Histamine increased from 6.3 +/- 1.5 to 89 +/- 15.5 ng/ml (p < 0.001), ECP increased from 20.6 +/- 6.4 to 237.1 +/- 50.2 ng/ml (p < 0.001), and tryptase increased from 2.34 +/- 0.6 to 9.7 +/- 2.3 U/ml (p < 0.001). Most samples did not have detectable quantities of MIP-1 alpha or RANTES. We also found a correlation between the level of MCAF/MCP-1 and IL-8 and the level of histamine or IL-8 and ECP. Our results suggest that the chemokines MCAF/MCP-1 and IL-8 may participate in the pathogenesis of allergic rhinitis, contributing to the attraction of the proinflammatory cells and mediator release, which might be very important during the late phase of the allergic reaction. Furthermore, the ratio of certain chemokines, such as MCAF/MCP-1 and IL-8 may reflect the magnitude of the reaction, as does the presence of histamine and ECP.

Beta 2-integrins in different forms of urticaria

As urticarial lesions involve tissue invasion by inflammatory cells, and as beta 2-integrins play a central part in adhesion of leucocytes to endothelia, allowing their migration into the tissues, we have explored the distribution and sequential expression of these molecules in tissue sections from different forms of urticaria. Prick test weals (of 10 min duration) to common inhalant allergens showed only a minor increase of CD18, whereas in a case of cold urticaria CD11b and CD18 molecules were increasingly upregulated within the first 30 min after elicitation of the lesions. Skin test sites in delayed pressure urticaria, and urticarial lesions (> 6 h duration) of acute and chronic recurrent urticaria also showed marked upregulation of CD11b and CD18, and to a lesser extent of CD11a, but this did not strongly correlate with the intensity of the mixed cellular infiltrate. Non-lesional skin showed expression of beta 2-integrins in chronic urticaria, delayed pressure urticaria, and less so in acute urticaria, suggesting generalized leucocyte activation. This analysis of integrins thus suggests an early and extensive involvement of these molecules in the pathological events associated with the evolution of urticarial lesions.

The association of individual allergen reactivity with respiratory disease in a national sample: data from the second National Health and Nutrition Examination Survey, 1976-80 (NHANES II)

The independent association of individual allergen reactivity with respiratory disease was evaluated with use of the second National Health and Nutrition Examination Survey, a sample of the U.S. white civilian population, ages 6 to 24 years (n = 4295). Eight, 1:20 wt/vol, 50% glycerol, unstandardized extracts were administered by prick puncture. Allergen reactivity was reported as the percent with a mean erythema diameter 10.5 mm or greater at 20 minutes. Only the prevalence of asthma and allergic rhinitis increased with the increasing number of positive allergen skin tests. The independent association of individual allergen reactivity with respiratory disease was quantified with logistic models that included other allergen reactivity, age, sex, smoking, and region. Asthma was associated with reactivity to house dust (odds ratio, 2.9; 95% confidence interval [CI] 1.7 to 5) and Alternaria (odds ratio, 5.1; 95% CI: 2.9 to 8.9). Allergic rhinitis was associated with reactivity to ragweed (odds ratio, 2.3; 95% CI: 1.5 to 3.3); ryegrass (odds ratio, 2.8; 95% CI: 1.8 to 4.3); house dust (odds ratio, 2.5; 95% CI: 1.6 to 3.9); Alternaria (odds ratio, 2.3; 95% CI: 1.5 to 3.4). Asthma only (without allergic rhinitis) was associated with dust and Alternaria. Allergic rhinitis only (without asthma) was associated with ryegrass, ragweed, and house dust. When both asthma and allergic rhinitis were present, only house dust and Alternaria remained associated. These findings highlight the association of specific allergens with upper and lower respiratory diseases and the interactions among coexisting respiratory diseases.

The role of eosinophils in the pathophysiology of asthma

From current information, a number of conclusions can be drawn. Antigen activation of the allergic reaction in the airways is associated with an immediate rise in mast cell derived mediators, including histamine and tryptase. Associated with antigen activation of the allergic reaction is recruitment of eosinophils to the airways. This can best be seen in the airway lavage 48 hours after challenge with antigen. An increased presence of eosinophils suggests that they are an important contributor to the late allergic reaction and may be one of the major constituents in the development of bronchial inflammation. Although many factors participate in the late allergic inflammatory response, eosinophil-derived proteins are known to cause airway injury. Regulation of eosinophils in this process is not clearly established; however, our findings of increased IL-5 in relationship to the presence of eosinophils and their granular proteins suggests that this cytokine may be an important modulator of eosinophil function and activation following allergen challenge. However, much remains unknown in understanding bronchial inflammation and the eosinophil's role in the process. In conclusion, the eosinophil is a major cellular participant in late phase allergic airway disease. Its presence and known functions suggest that the eosinophil is a significant cellular factor in the development of allergic airways disease in asthma. Further advances in this area will follow continued studies, particularly those which involve biopsy and correlation with airway physiology.

The role of basophils in asthma

The characteristics of the acute and late human response to antigen in the upper and lower airways and in the skin is summarized in TABLE 2. This table makes it clear that while mast cells are responsible for the mediator release of the acute phase, eosinophils and basophils are the cells involved in the mediator release which occurs during the experimental late phase reaction. The pattern of mediators observed during the acute response is quite characteristic of the mast cell. Thus, in the nose, skin, and lungs, the acute response is characterized by significant increases in histamine, PGD2, tryptase, and sometimes LTC4. In the late phase reaction, the pattern of mediator release is characteristic of basophils and eosinophils, and includes histamine, LTC4 (where measurable), and eosinophil-derived proteins, without PGD2 or tryptase. Basophils have been identified at appropriate time-points in each model using morphologic and phenotypic criteria, and their numbers relate to the histamine levels. Finally, treatment with glucocorticosteroids, the most potent drugs available for treating chronic allergic inflammation, obliterates the late phase reaction and decreases both mediator release and the infiltration of eosinophils and basophils. Chronic allergic inflammation is now taken by both the pulmonary and immunologic community as a hallmark of asthma, and it can be stated without equivocation that the basophils are responsible for the mediator release observed in that response.