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

Induction of mast cell accumulation by chymase via an enzymatic activity- and intercellular adhesion molecule-1-dependent mechanism

BACKGROUND AND PURPOSE

Chymase is a unique, abundant secretory product of mast cells and a potent chemoattractant for eosinophils, monocytes and neutrophils, but little is known of its influence on mast cell accumulation.

EXPERIMENTAL APPROACH

A mouse peritoneal inflammation model, cell migration assay and flowcytometry analysis, were used to investigate the role of chymase in recruiting mast cells.

KEY RESULTS

Chymase increased, by up to 5.4-fold, mast cell numbers in mouse peritoneum. Inhibitors of chymase, heat-inactivation of the enzyme, sodium cromoglycate and terfenadine, and pretreatment of mice with anti-intercellular adhesion molecule 1, anti-L-selectin, anti-CD11a and anti-CD18 antibodies dramatically diminished the chymase-induced increase in mast cell accumulation. These findings indicate that this effect of chymase is dependent on its enzymatic activity and activation of adhesion molecules. In addition, chymase provoked a significant increase in 5-HT and eotaxin release (up to 1.8- and 2.2-fold, respectively) in mouse peritoneum. Since 5-HT, eotaxin and RANTES can induce marked mast cell accumulation, these indirect mechanisms may also contribute to chymase-induced mast cell accumulation. Moreover, chymase increased the trans-endothelium migration of mast cells in vitro indicating it also acts as a chemoattractant.

CONCLUSION AND IMPLICATIONS

The finding that mast cells accumulate in response to chymase implies further that chymase is a major pro-inflammatory mediator of mast cells. This effect of chymase, a major product of mast cell granules, suggests a novel self-amplification mechanism for mast cell accumulation in allergic inflammation. Mast cell stabilizers and inhibitors of chymase may have potential as a treatment of allergic disorders.

Uremic pruritus: a review

Pruritus is a major disorder among the skin derangements in advanced renal failure. Its prevalence seems to be diminishing perhaps because of improvements in dialysis treatment. Recent information suggests that interactions between dermal mast cells and distal ends of nonmyelinated C fibers may be important in the precipitation and regulation of the sensory stimuli. The knowledge as to the control of pruritus transmission to cortex areas is still incomplete but endogenous opioid and opioid receptors may have a role in this regard. A recent classification was proposed for pruritus based on the level of its origin. Uremic pruritus, however, seems to be too complex to fit perfectly in any of the suggested modalities. Inflammation and malnutrition are recognized risk factors for cardiovascular death in end-stage renal disease patients, which may be related to the genesis of pruritus. Consistent with this concept, lower serum levels of albumin and higher serum levels of ferritin were found in pruritic patients when compared to nonpruritic ones. Newer treatments for this difficult clinical problem are being developed and tested.

Pruritic dermatoses: overview of etiology and therapy

This review begins with a brief survey of the neurophysiology and neuroanatomy of pruritus, and goes on to describe the etiology of the major allergic and nonallergic pruritic disorders. The etiology of pruritus often suggests the appropriate treatment. For example, urticaria, which is primarily mediated by histamine, is amenable to treatment with H1 antihistamines. Second-generation, nonsedating antihistamines appear to be more effective than sedating antihistamines, perhaps because of better compliance. Other systemic pharmacologic options may be useful in nonhistamine-mediated disorders, for example, immunomodulators for inflammation-induced pruritus or opiate antagonists for atopic dermatitis. Nonpharmacologic measures, such as proper skin care, and physical modalities, such as phototherapy or acupuncture, may also be helpful.

Cetirizine inhibits skin reactions but not mediator release in immediate and developing late-phase allergic cutaneous reactions. A double-blind, placebo-controlled study

BACKGROUND

Recent reports have indicated cetirizine, a potent H(1)-receptor antagonist, to possess a number of anti-inflammatory effects, e.g. inhibition of mast cell degranulation and inhibition of leucocyte migration and activation.

OBJECTIVE

The aim of this study was to compare the effects of cetirizine on skin responses and mediator release in intact skin in immediate and developing late-phase allergic reactions by microdialysis technique.

METHODS

Cetirizine 10 mg once daily or matching placebo were administered to 10 atopic subjects for 6 days followed by a 2-week washout in a randomized, double-blind, placebo-controlled, cross-over trial. Immediate skin test responses to allergen, codeine, and histamine and late-phase reactions to allergen were assessed. The time course of extracellular levels of inflammatory mediators in intact skin were monitored by microdialysis techniques using 2 kDa and 3 MDa cut-off fibers, respectively.

RESULTS

Cetirizine significantly reduced immediate weal and flare reactions to allergen, codeine, and histamine. Injection of allergen, but not buffer controls, induced a significant release of histamine, tryptase, prostaglandin D(2), total protein, and eosinophilic cationic protein. No significant increase of leukotriene B(4) and myeloperoxidase was observed. Cetirizine inhibited early total protein extravasation by 40%, but this did not reach a significant level. None of the inflammatory mediators were significantly inhibited by cetirizine. Cetirizine significantly reduced the late-phase skin induration to allergen by approximately 30%.

CONCLUSION

Cetirizine potently reduced skin responses in immediate allergic reactions without inhibition of early mediators. These data indicate cetirizine to be a potent H1-receptor antagonist with no effect on mast cell activation. It did not inhibit any of the late-phase mediators, but it reduced the late skin reaction. These data suggest that mediators other than those actually measured may play a significant role in the clinical late-phase reaction.

New insights into the second generation antihistamines

Second generation antihistamines are recognised as being highly effective treatments for allergy-based disease and are among the most frequently prescribed and safest drugs in the world. However, consideration of the therapeutic index or the benefit/risk ratio of the H1 receptor antagonists is of paramount importance when prescribing this class of compounds as they are used to treat non-life threatening conditions. There are many second generation antihistamines available and at first examination these appear to be comparable in terms of safety and efficacy. However, the newer antihistamines in fact represent a heterogeneous group of compounds, having markedly differing chemical structures, adverse effects, half-life, tissue distribution and metabolism, spectrum of antihistaminic properties, and varying degrees of anti-inflammatory effects. With regard to the latter, there is growing awareness that some of these compounds might represent useful adjunct medications in asthma therapy. In terms of safety issues, the current second generation grouping includes compounds with proven cardiotoxic effects and others with the potential for adverse drug interactions. Moreover, some of the second generation H1 antagonists have given cause for concern regarding their potential to cause a degree of somnolence in some individuals. It can be argued, therefore, that the present second generation grouping is too large and indistinct since this was based primarily on the concept of separating the first generation sedating compounds from nonsedating H1 antagonists. Although it is too early to talk about a third generation grouping of antihistamines, future membership of such a classification could be based on a low volume of distribution coupled with a lack of sedating effects, drug interactions and cardiotoxicity.

Selective effect of levocabastine on histamine receptor and histamine release from human leukocytes and guinea pig isolated tissue

BACKGROUND

Levocabastine is a potent histamine H1 receptor antagonist used topically in the treatment of patients with allergic rhinitis. It has been suggested that antihistamines also have anti-inflammatory properties.

OBJECTIVE

The present study was performed to investigate whether levocabastine, in addition to the anti-H1 receptor activity, has anti-inflammatory properties and thus is able to modulate the release of histamine and cytokines, such as interleukin 5 from human leukocytes and isolated tissues.

METHODS

Leukocytes suspensions were prepared by dextran sedimentation of peripheral venous blood drawn from allergic and healthy volunteers. Leukocytes obtained from allergic volunteers were preincubated for 30 minutes with levocabastine (doses 10(-8) M to 10(-6) M) and thereafter incubated with allergen. Leukocytes obtained from healthy volunteers were incubated for zero to three hours with levocabastine (doses 10(-14) M to 10(-3) M). Histamine release was measured by an automated fluorometric method. Interleukin-5 release was measured by enzyme linked immunoassay. Contractile responses to histamine on guinea pig trachea and lung parenchyma as well as the release of histamine and interleukin-5 by the tissues were investigated in the absence or presence of levocabastine and/or the histamine H2 receptor antagonist cimetidine.

RESULTS

Levocabastine did not influence allergen-induced histamine release from leukocytes obtained from allergic volunteers. High concentrations (10(-4)and 10(-3) M) of levocabastine, however, caused release of histamine from leukocytes obtained from healthy volunteers as well as guinea pig airway smooth muscle tissues. Pretreatment with levocabastine dose-dependently decreased the contractile response to histamine, showing an irreversible competitive mechanism. Interleukin 5 release from human leukocytes and by guinea pig airway smooth muscle was not detectable.

CONCLUSIONS

These findings indicate that the H1 receptor blocker, levocabastine, has probably no anti-inflammatory properties, measured as histamine release, and that the histamine release from both human leukocytes and guinea pig trachea and lung parenchyma is significantly increased by the drug only at high concentrations.

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)