The many faces of systemic mastocytosis.

OBJECTIVE: This short review article will augment the reader's knowledge of mast cell physiology and will offer an overview of current information on the pathophysiology, heterogeneity, and treatment of human mastocystosis. DATA SOURCES AND STUDY SELECTION: Articles published since 1980, textbooks, information from computerized databases, references identified from bibliographies of relevant articles, and books published in the last 10 years. RESULTS AND CONCLUSIONS: Mastocytosis is a complex disease with a multitude of clinical presentations, often misdiagnosed, which can embrace characteristics of other diseases and generate a chameleon-like picture. Mast cells possess many important physiologic functions in the human body, but as a consequence of poorly understood events, they can also start a cascade of pathologic reactions. Although a great deal is known about mechanisms involved in physiologic and pathologic processes of mast cells, many areas are waiting to be explored in this millennium.

Absorption, distribution, metabolism, and excretion of a respirable antisense oligonucleotide for asthma.

EPI-2010 is a respirable antisense oligonucleotide (RASON), which selectively attenuates discordantly overexpressed adenosine A(1) receptors in allergic lung (Nature 1997;385:721). In the present study, aerosolized [(35)S]-labeled EPI-2010 (5 mg exposure; specific activity 0.055 Ci/mmol) was administered to normal rabbits by endotracheal tube to assess biodistribution, route of elimination, and potential cardiovascular toxicity. The animals were killed at 0, 6, 24, 48, and 72 h after inhalation of EPI-2010. Duplicate aliquots from different tissues and samples were solubilized and assessed for radioactivity. Approximately 1.4% of the total aerosolized EPI-2010 was deposited into the lung. The concentration of the drug in the lung at 0, 6, 24, 48, and 72 h was 64.0 +/- 1.5, 67.0 +/- 4.4, 32.0 +/- 3.7, 23.4 +/- 1.4, and 2.1 +/- 0.5 microg equivalents, respectively. Only a small amount of the radioactivity was detected in extrapulmonary tissues. By 72 h, 67.5% of the administered dose was excreted in the urine, which represented the major pathway of elimination. In postlabeling studies, intact full-length EPI-2010 could only be detected in the lung. Autoradiographic analysis after inhalation of [(35)S]-labeled EPI-2010 showed a relatively uniform deposition of drug throughout the lung. The aerosolized EPI-2010 did not have any significant systemic effects on the cardiovascular system as determined by Cardiomax-II analysis. This pattern of distribution and the lack of effect on cardiovascular function support the concept that RASONs offer the potential to safely address respiratory targets for which systemic distribution and systemic bioavailability may be contraindicated.

Treatment of allergic asthma with monoclonal anti-IgE antibody. rhuMAb-E25 Study Group.

BACKGROUND: Immune responses mediated by IgE are important in the pathogenesis of allergic asthma. A recombinant humanized monoclonal antibody (rhuMAb-E25) forms complexes with free IgE and blocks its interaction with mast cells and basophils. We studied the efficacy of rhuMab-E25 as a treatment for moderate-to-severe allergic asthma. METHODS: After a 4-week run-in period, we randomly assigned 317 subjects (age range, 11 to 50 years) who required inhaled or oral corticosteroids (or both) to receive either placebo or one of two regimens of rhuMAB-E25: high-dose rhuMAb-E25 (5.8 microg per kilogram of body weight per nanogram of IgE per milliliter or low-dose rhuMAb-E25 (2.5 microg per kilogram per nanogram of IgE per milliliter) intravenously on days 0 (half a dose), 4 (half a dose), and 7 (full dose) and then once every 2 weeks thereafter for 20 weeks. For the first 12 weeks of the study, the subjects continued the regimen of corticosteroids they had received before enrollment. During the following eight weeks, the doses of corticosteroids were tapered in an effort to discontinue this therapy. The primary outcome measure was an improvement in the asthma symptom score at 12 weeks, according to a 7-point scale, in which a score of 1 indicated no symptoms and a score of 7 the most severe symptoms. RESULTS: A total of 106 subjects were assigned to receive a high dose of rhuMAb-E25, 106 were assigned to receive a low dose, and 105 were assigned to receive placebo. At base line, the mean asthma symptom score was 4.0. After 12 weeks of therapy, the mean (+/-SE) scores were 2.8+/-0.1 in the high-dose group (P=0.008) and 2.8+/-0.1 in the low-dose group (P=0.005), as compared with 3.8+/-0.1 in the placebo group. At 20 weeks, the mean scores were 2.7+/-0.1 in both the high-dose group (P=0.048) and the low-dose group (P=0.14), as compared with 2.9+/-0.1 in the placebo group. More subjects in the two rhuMAb-E25 groups were able to decrease or discontinue their use of corticosteroids than in the placebo group, but only some of the differences were significant. After 20 weeks, serum free IgE concentrations decreased by a mean of more than 95 percent in both rhuMAb-E25 groups. The therapy was well tolerated. After 20 weeks, none of the subjects had antibodies against rhuMAb-E25. CONCLUSIONS: A recombinant humanized monoclonal antibody directed against IgE has potential as a treatment for subjects with moderate or severe allergic asthma.

Oligonucleotide therapy of allergic asthma.

The recent increase in the prevalence of and mortality from asthma has inspired several new molecular techniques to improve treatment. Because asthma is a disease of gene polymorphism, gene therapy is unlikely to be effective. Alternative methods use oligonucleotides (ODNs) in the form of (1) DNA vaccination expressing CpG motifs that mimic bacterial DNA or (2) antisense ODNs inhaled and locally deposited into pulmonary airways to specifically modulate receptors for inflammatory mediators. DNA vaccination, a form of "molecular immune surveillance," attenuates a TH2 predominance. Antisense directed against the adenosine A(1 ) receptor abrogates A(1 ) sensitivity, improves allergen-induced immediate airway obstruction, and inhibits the expected increase in histamine responsiveness in allergic rabbits. Adenosine receptor inhibition lasts for an average of 7 days and the majority of the antisense remains in the lung. ODN therapy for asthma seem unlimited, but confirmation awaits the extension from animal models to human studies.

Administration of budesonide once daily by means of turbuhaler to subjects with stable asthma.

BACKGROUND: Optimal management of chronic, mild-to-moderate asthma with inhaled steroids may include use of the lowest possible doses, as recommended in guidelines, and a reduction in the frequency of daily administration for greater convenience. Lower doses and once daily treatment with inhaled steroids must be rigorously evaluated in controlled clinical trials. OBJECTIVES: The objective of this study was to assess the efficacy and safety of once daily treatment with budesonide in subjects with stable asthma. METHODS: Once daily budesonide was assessed in 309 adult subjects, including those who were and were not using an inhaled steroid at baseline. The subjects were stratified by inhaled steroid use and randomly assigned to one of 3 treatments: 200 microgram budesonide, 400 microgram budesonide, or placebo administered by means of Turbuhaler once daily in the morning for 6 weeks. Beyond this point, treatment was continued unchanged for another 12 weeks (maintenance) in those receiving 200 microgram budesonide once daily and placebo. In those who received 400 microgram budesonide once daily, the dose was reduced to 200 microgram once daily at week 6 and held constant for the remaining 12 weeks (400/200 microgram group). Primary efficacy endpoints were mean change from baseline in FEV1 and morning peak expiratory flow. RESULTS: Once daily budesonide was well tolerated and resulted in significant improvements in all efficacy endpoints, even though baselines were well stabilized. Baseline lung function was elevated with little room for improvement; however, mean increases in FEV1 during the maintenance period were 0.10 L and 0.11 L in the 200 microgram and 400/200 microgram groups, respectively, versus a decrease of -0.09 L in the placebo arm (P <.001). Results for peak expiratory flow were similar. Significant improvements in secondary endpoints, including symptoms, beta-agonist use, and quality of life, also developed with budesonide 200 and 400 microgram once daily. CONCLUSION: Inhaled budesonide, in doses as low as 200 microgram, may be an appropriate introductory or maintenance dose in subjects with stable, mild-to-moderate asthma.

Respirable antisense oligonucleotide (RASON) therapy for allergic asthma.

A new technology for treating respiratory disease, respirable antisense oligonucleotides (RASONs), has recently been developed by our group. RASONs are short, single-stranded nucleic acids, generally modified to reduce degradation. They differ from traditional drugs, which usually antagonise preformed proteins already functioning in a disease process. Instead, RASONs can attenuate the expression of disease-associated genes by targeting the messenger RNA (mRNA). Delivered directly to the target tissue, the lung, they avoid the problems of ineffective delivery encountered by other routes of administration. When an adenosine A(1) antisense oligonucleotide was delivered to the lungs of allergic rabbits with up-regulated A(1) adenosine receptors, desensitisation to the bronchoconstrictor effects of adenosine, histamine and a common aeroallergen (dust mite) occurred. The effect on A(1) receptors persisted on average for nearly 7 days. RASON (the phosphorothioate antisense oligonucleotide EPI-2010) administered in low dosage was evenly distributed throughout the lung (with no detectable systemic active metabolites), and was excreted primarily in urine. These results demonstrate that RASONs can be efficiently and effectively delivered to the peripheral lung. They potently and selectively attenuate the expression of disease-associated genes, an approach to therapy which is now being extended to other potentially important mediators of bronchial asthma.

Immunoregulatory roles of IL-10 in innate immunity: IL-10 inhibits macrophage production of IFN-gamma-inducing factors but enhances NK cell production of IFN-gamma.

In our study of the immunoregulatory roles of IL-10 in innate immunity, nonantigenic phagocytosable chitin particles were administered i.v. to IL-10-deficient (knockout (KO)) mice or KO mice pretreated with anti-NK1.1 or anti-IFN-gamma Abs. The results established that chitin treatment of KO mice increased superoxide anion release from alveolar macrophages (Mphi) to a level much higher than that in wild-type (WT) mice. The results also suggested that the NK cell is the source of IFN-gamma that is primarily responsible for this alveolar Mphi priming. To further study the roles of IL-10-inhibiting chitin-induced IFN-gamma production, we used spleen cell cultures. The experiments showed that IL-12, IL-18, and TNF-alpha, which were produced by chitin-stimulated Mphi, contributed to the IFN-gamma-inducing activity of chitin. Our results established that exogenous IL-10 inhibited chitin-induced IFN-gamma production in spleen cell cultures from both KO and WT mice. Exogenous IL-10 also inhibited IL-12 and TNF-alpha production by chitin-stimulated Mphi. Exogenous IL-10 decreased IL-12- or IL-18-induced IFN-gamma levels in KO but not in WT NK cell cultures. However, exogenous IL-10 enhanced IFN-gamma levels when NK cells were stimulated simultaneously with both IL-12 and IL-18 in KO and WT cultures. Our in vitro data indicate that IL-10 has differential effects on chitin-induced IFN-gamma production. However, the inhibitory effects of endogenous IL-10 appear to be dominant in the chitin-induced alveolar Mphi priming response in vivo.

Adenosine receptor-mediated relaxation of rabbit airway smooth muscle: a role for nitric oxide.

In this study, we investigated the relaxant effect of adenosine receptor agonists on KCl-precontracted airway smooth muscle from rabbits and characterized the type of receptor involved in bronchorelaxation in the presence and absence of epithelium. We further defined the role of epithelium-derived relaxing factor, i.e., nitric oxide (NO), on these responses. In both epithelium-intact and -denuded tertiary airway rings from rabbits, the adenosine receptor agonists 2-[p-(2-carboxyethyl)]phenylethylamino-5-N'-ethylcarboxamidoadenos ine (CGS-21680), 5'-(N-ethyl-carboxamido)adenosine (NECA), 2-chloroadenosine (CAD), and (-)-N6-(2-phenylisopropyl)adenosine (R-PIA) relaxed airway smooth muscle with a potency order of CGS-21680 > NECA > CAD > R-PIA. A 98.5, 89.7, 73.2, and 64.7% relaxation was observed at 10(-5) M by CGS-21680, NECA, CAD, and R-PIA in the epithelium-intact bronchial rings, respectively. The 50% maximum effective concentration (EC50; x 10(-7) M) values for CGS-21680, NECA, CAD, and R-PIA were 2, 4, 9, and 80, respectively. Denuded rings, however, showed much less relaxant responses to various adenosine agonists compared with epithelium-intact rings. The adenosine receptor antagonist 8-(sulfophenyl)theophylline significantly attenuated the relaxant responses to all the agonists in the epithelium-intact and -denuded rings. The epithelium-dependent relaxant effect of the agonists in airway rings was inhibited by NG-monomethyl-L-arginine (L-NMMA; 30 microM). The EC50 (x 10(-6) M) values for CGS-21680, NECA, CAD, and R-PIA in the presence of inhibitor were 5.5, 8, 30, and 200, respectively. The L-NMMA produced an insignificant inhibitory effect in the epithelium-denuded rings. L-Arginine but not D-arginine (100 microM) reversed the inhibitory effect of L-NMMA on adenosine agonist-induced relaxation. In primary epithelial cells in culture, CGS-21680 (10(-5) M) induced a fourfold increase in NO production over the control. The CGS-21680-induced NO production in epithelial cells was significantly inhibited by NG-nitro-L-arginine methyl ester (L-NAME). Moreover, L-arginine reversed the inhibitory effect of L-NAME in the epithelial cells. The data suggest that adenosine relaxes rabbit airway smooth muscle through an A2 adenosine receptor and the epithelium serves as a source of NO.

Chitin particle-induced cell-mediated immunity is inhibited by soluble mannan: mannose receptor-mediated phagocytosis initiates IL-12 production.

Previous studies showed that mouse spleen cells produced IL-12, TNF-alpha, and IFN-gamma when stimulated with phagocytosable-size chitin particles (N-acetyl-D-glucosamine polymers). To dissect the mechanisms of the cytokine production in this study, spleen cells from BALB/c mice were cultured with 1 to 10 microm chitin particles, heat-killed Corynebacterium parvum vaccine, zymosan, and mannan (a mannose polymer)-coated latex beads (1 microm) at 1, 10, or 100 microg/ml. We found that these particles induced IL-12, TNF-alpha, and IFN-gamma. However, these cytokines were not produced when spleen cells were cultured with soluble chitin, mannan, or laminarin (a polymer of beta-glucan), 1 to 10 microm beta-glucan particles, laminarin-coated latex beads, 1 microm latex beads, 50 to 100 microm chitin particles, or 50 to 100 microm mannan-coated beads. Soluble mannan, but not soluble laminarin, inhibited cytokine production following stimulation with 1 to 10 microm chitin particles, zymosan, or heat-killed C. parvum. In addition, cytochalasin D also inhibited cytokine production. The treatments with soluble mannan or with cytochalasin D, in sharp contrast, did not inhibit LPS-induced IL-12/IFN-gamma production or exogenous IL-12-induced IFN-gamma production. Finally, spleen cells from C3H/HeJ mice also showed comparable levels of IL-12/TNF-alpha/IFN-gamma production when induced by 1 to 10 microm chitin particles. Taken together, our results indicate that mannose receptor-mediated phagocytosis, but not the receptor-mediated pinocytosis, is highly associated with the production of IFN-gamma-inducing extracellular signaling factors such as IL-12 and TNF-alpha. The novel mechanism of phagocytosis-dependent IL-12 production appears to be distinct from that of LPS-induced cytokine production.

Alveolar macrophage priming by intravenous administration of chitin particles, polymers of N-acetyl-D-glucosamine, in mice.

Intravenous (i.v.) administration of phagocytosable chitin particles (1 to 10 microm) in C57BL/6 mice and SCID mice primed alveolar macrophages (Mphi) within 3 days to yield up to a 50-fold increase in their oxidative burst when elicited in vitro with phorbol myristate acetate (PMA). C57BL/6 mice pretreated with monoclonal antibodies (MAbs) against mouse gamma interferon (IFN-gamma) or NK1.1 showed a markedly decreased level of alveolar Mphi priming following injection of chitin particles. To confirm IFN-gamma production in vitro, spleen cells isolated from normal C57BL/6 mice and SCID mice were cultured with chitin particles. Significant IFN-gamma production was observed following stimulation with chitin but not with chitosan or latex beads. When spleen cells were treated with anti-NK1.1 MAb, IFN-gamma production was significantly inhibited. Another set of experiments showed that when C57BL/6 mice were pretreated i.v. with a small dose IFN-gamma, a higher level of priming was induced with not only phagocytosable chitin particles but also phagocytosable chitosan and even latex beads. Likewise, the spleen cell cultures preconditioned with IFN-gamma provided an up-regulation of IFN-gamma production by these phagocytosable particles. Taken together, the in vivo and in vitro results suggest that (i) the alveolar Mphi priming mechanism is due, at least in part, to direct activation of Mphi by IFN-gamma, which is produced by NK1.1+ CD4- cells; (ii) IFN-gamma would have an autocrine-like effect on Mphi and make them more responsive to particle priming; and (iii) phagocytosis of particulates, probably by a postmembrane event such as interiorization, appears to be important for the up-regulation of alveolar Mphi priming and IFN-gamma production.

DNA antisense therapy for asthma in an animal model.

Asthma is an inflammatory disease characterized by bronchial hyper-responsiveness that can proceed to life-threatening airway obstruction. It is one of the most common diseases in industrialized countries, and in the United States accounts for about 1% of all healthcare costs. Asthma prevalence and mortality have increased dramatically over the past decade, and occupational asthma is predicted to be the pre-eminent occupational lung disease in the next decade. Increasing evidence suggests that adenosine, an endogenous purine that is involved in normal physiological processes, may be an important mediator of bronchial asthma. In contrast to normal individuals, asthmatic individuals respond to adenosine challenge with marked airway obstruction, and concentrations of adenosine are elevated in the bronchoalveolar lavage fluid of asthma patients. We performed a randomized crossover study using the dust mite-conditioned allergic rabbit model of human asthma. Administration of an aerosolized phosphorothioate antisense oligodeoxynucleotide targeting the adenosine A1 receptor desensitized the animals to subsequent challenge with either adenosine or dust-mite allergen.

Immunomodulatory effects of IL-12 on allergic lung inflammation depend on timing of doses.

We investigated the effects of IL-12 on a murine model of allergic lung inflammation. Administration of IL-12 was timed to interfere with either allergic sensitization (early dosage) or the hypersensitivity inflammatory response in the lung (late dosage), or both (early and late dosages). Comparisons of IL-12- and PBS-treated animals within each treatment group revealed several noticeable effects of IL-12. Early dosage, and the combination of early and late dosages, strikingly decreased ragweed-specific serum IgE, tracheal ring reactivity to acetylcholine, and BAL eosinophilia following allergen challenge. In contrast, late dosage had no effect on IgE levels and only a minimal effect on tracheal ring reactivity, but had a modest effect on recruitment of eosinophils. Early dosage down-regulated IL-5 and IL-10, but did not alter IL-4 or IFN-gamma expression. Late dosage down-regulated IL-5, up-regulated IL-10 and IFN-gamma, but did not change IL-4 expression. The combination of early and late dosage down-regulated IL-4, IL-5, and IL-10 expression, but increased IFN-gamma expression and production in the BAL cells and fluids. Taken together, these results indicate that IL-12 has potent immunomodulatory effects on allergic lung inflammation that depend on the timing of IL-12 administration relative to allergic sensitization and allergen challenge.

Simultaneous measurement of cyclopentyladenosine-induced contraction and intracellular calcium in bronchial rings from allergic rabbits and it's antagonism.

We reported previously that adenosine is a specific contractile agonist in the asthmatic airways of allergic rabbits; cyclopentyladenosine (CPA) was the most potent bronchoconstrictor in this model. The aim of the present investigation was to examine the contracting effect of CPA, an A1 adenosine receptor agonist, in relation to the role of intracellular calcium ([Ca++]i) in airway smooth muscle of allergic rabbits in the presence and absence of extracellular calcium (Ca++). The effects of adenosine receptor antagonists theophylline (xanthine) and CGS-15943 (nonxanthine) were also evaluated on these responses. CPA (10(-9)-10(-4) M) produced a dose-dependent contraction of tertiary airway smooth muscle of allergic rabbits. An increase in tension of airway smooth muscle was accompanied by a quantitative increase in [Ca++]i in the presence of extracellular Ca++. CGS-21680, an A2 agonist, produced only marginal changes in force and [Ca++]i compared with CPA. The CPA-induced contraction as well as changes in [Ca++]i were significantly inhibited by both antagonists at a concentration of 10(-7) M. CGS-15943 and theophylline changed the EC50 values for the force from 1.1 x 10(-7) M to 2.3 x 10(-6) M and 1.0 x 10(-6) M, respectively. In Ca(++)-free medium, CPA (10(-4) M) induced only a 15 to 20% contraction compared with Ca(++)-containing medium. The changes in [Ca++]i were also reduced accordingly. CGS-15943 significantly inhibited the CPA-induced tension and changes in [Ca++]i whereas theophylline failed to inhibit these responses. 8-Cyclopentyl-1,3-dipropylxanthine, an A1-specific and potent antagonist, also did not inhibit the CPA-induced force and [Ca++]i in a separate set of experiments. The tertiary airway smooth muscle rings from age-matched normal rabbits did not respond to CPA and there was no detectable change in [Ca++]i. These data suggest that the asthmatic airway smooth muscle contraction has both extracellular Ca(++)-dependent and -independent components and the Ca(++)-independent component is xanthine insensitive.

Bioelectric response of human nasal epithelial cells to polycationic protein.

Polycationic proteins alter electrolyte transport by epithelium and endothelium, and in asthma are thought to disrupt the airway epithelium and contribute to hyperresponsiveness and airway plugging. In the present study, we used primary cultures of human nasal epithelial cells to investigate the response of respiratory tract epithelium to luminal presentation of a polycationic protein, protamine. Protamine (100 micrograms/ml) in the apical bathing solution had no significant effect on basal transepithelial resistance (Rt) but decreased short-circuit current (Isc) and hyperpolarized the apical membrane, indicating that Na+ absorption had been inhibited. Pretreating with amiloride inverted the response to protamine, resulting in an increase in Isc, depolarization of the apical membrane, and decrease in the fractional resistance of the apical membrane (fRa). The increase in Isc was inhibited by pretreatment with bumetanide. These results indicated that protamine augmented amiloride-induced Cl- secretion. Induction of Cl- secretion by bathing the apical surface in 3 mM Cl(-)-Ringer solution similarly resulted in protamine-induced depolarization of the apical membrane. Heparin precipitated protamine from solution and reversed the Isc responses. In summary, low concentrations of polycationic protein can alter electrolyte transport by human airway epithelium without desquamation, and the response is dependent on the secretory state of the tissue.

A role for Th2 T-memory cells in early airway obstruction.

The role of T-cell memory in late-phase allergic lung inflammation is not well defined. To evaluate the role of systemic T-cell memory in allergic late-phase lung inflammation, BALB/c mice were injected intraperitoneally with ovalbumin (OVA) or ragweed (RW) allergens (Test I and Test II groups) or saline (control groups C I and C IV) and then challenged intratracheally with the allergen. Late-phase allergic lung inflammation was defined by: (i) recruitment of eosinophils to airways, (ii) IL-5 mRNA upregulation in BAL fluid cells, and (iii) detection of a Th2 cell cytokine profile in BAL fluids. The number of eosinophils recruited in allergic mice following intratracheal challenge with allergen was at least 300-fold higher P < or = 0.01) in mice with allergen-specific T-memory cells in BAL fluid (Test I and Test II) than in control mice without allergen-specific T-memory cells (C I and C IV). Further, the number of eosinophils recruited in Test I and II correlated with the magnitude of in vitro T-cell memory responses (r = 0.93, P < or = 0.04). Moreover, IL-5 mRNA upregulation in BAL cells and Th2 cytokine production in BAL fluids were observed only in Test I and Test II, and not in any of the control groups. Further, results from pulmonary function tests performed on the same allergic animals indicated that only animals from Test I and Test II groups had impaired lung function after allergen challenge. Taken together, these data strongly suggest that allergen-specific Th2-type T-cell memory is required for the development of allergic asthma. That is, without T-cell memory responses, no eosinophil recruitment and release of EPO (which is known to induce bronchoconstriction) occurred in the airways, and no Th2 cytokine profile was detected in the BAL fluid. Furthermore, if the Th2 cytokine profile was absent, then pulmonary functions remained normal.

Nasal pathology and ultrastructure in patients with chronic airway inflammation (RADS and RUDS) following an irritant exposure.

BACKGROUND: Reactive airways dysfunction syndrome is a chronic asthma-like condition developing after an acute irritant exposure, and chronic inflammation has been seen on endobronchial biopsy. Reactive upper-airways dysfunction syndrome is chronic rhinitis developing in temporal association with a toxic inhalation exposure, but the pathophysiology is unknown. OBJECTIVES: To study biopsies of the nasal mucosa in patients with reactive upper-airways dysfunction syndrome and in some cases reactive airways dysfunction syndrome developing in temporal association with a chlorine dioxide exposure, to see if a histologic basis for the persistent rhinitis and sensitivity to chemical irritants could be determined. METHODS: Specimens were stained with hematoxylin-eosin and immunoperoxidase stains for substance P, vasointestinal peptide, and S-100 (nerve fibers), and fixed in glutaraldehyde for electron microscopy. Biopsies of three nonexposed subjects were performed for comparison. A pathologist blinded to clinical data interpreted the specimens. RESULTS: Inflammation ratings of exposed individuals were higher than for the nonexposed individuals. The number of nerve fibers stained was greater for patients vs controls. Substance P and vasointestinal peptide staining was nonspecific. Electron microscopy showed desquamation of the epithelium and permeability of epithelial cell junctions. CONCLUSION: This study suggests a mechanism by which ongoing low level exposures perpetuate airway inflammation after an inducing toxic inhalation. A possible overlap between reactive airways dysfunction syndrome, reactive upper-airway dysfunction syndrome and the multiple chemical sensitivity syndrome is suggested.

Adenosine-induced bronchoconstriction and contraction of airway smooth muscle from allergic rabbits with late-phase airway obstruction: evidence for an inducible adenosine A1 receptor.

Recently, there has been an increasing interest in adenosine as a potential mediator of allergic asthma. In the present study, we used the allergic rabbit model developed in our laboratory to study the airway responses to adenosine and receptor binding in allergic lung vs. normal. Neonatal, pathogen-free rabbit litter mates were injected intraperitoneally within 24 hr of birth with ragweed pollen extract (1 mg/ml) to produce preferentially allergen-specific immunoglobulin E. Immunization produced bronchial airway hyperresponsiveness. Aerosolized adenosine (0.156-10 mg/ml) caused a dose-dependent bronchoconstriction (PC50 adenosine = 1.64 +/- 0.84 mg/ml). 9-Chloro-2-(2-furyl)[1,2,4]triazole[1,5- c]quinazolin-5-amine (CGS-15943), a nonxanthine adenosine receptor antagonist, significantly inhibited the adenosine-induced airway obstruction in term of dynamic compliance (P < .05). Adenosine also increased the lung resistance in a dose-dependent manner which was significantly inhibited by CGS-15943 (P < .05). Nonimmunized, pathogen-free, age-matched rabbits (control) did not respond to adenosine at these same concentrations. Adenosine also produced a concentration-dependent (10(-9)-10(-4) M) contraction of isolated tracheal and bronchial airway rings in vitro from allergic rabbits but had no detectable effect on normal rabbit airway smooth muscle. Peripheral airway smooth muscles (secondary and tertiary) were more responsive to adenosine than central (tracheal) airways. The contraction produced by 10(-4) M adenosine in primary, secondary and tertiary airways was 90, 135 and 265% of the contraction produced by 50 mM KCl, respectively. CGS-15943 (10(-7) M) significantly inhibited the adenosine-induced contraction (P < .05) shifting the dose-response curve to the right.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine receptor-mediated bronchoconstriction and bronchial hyperresponsiveness in allergic rabbit model.

Recently, there has been an increasing interest in adenosine as a potential mediator of allergic asthma. In the present study, we have employed an allergic rabbit model of late-phase asthma to characterize the adenosine receptor subtype in the asthmatic airways. The allergic rabbit model has physiological characteristics and pharmacological sensitivity comparable to human asthma. Adenosine causes a dose-dependent bronchoconstriction in allergic, but not in normal, rabbits. This adenosine-induced bronchoconstriction is significantly inhibited by theophylline, an adenosine receptor antagonist, thus suggesting the involvement of adenosine receptor(s). 5'-(N-ethylcarboxyamido) adenosine (NECA), a nonselective agonist, 2-[p-(2-carboxyethyl)-phenethylamino]-5'-(N-ethylcarboxamido)-aden osine (CGS-21680), an A2-selective receptor agonist, and cyclopentyl adenosine (CPA), an A1-selective agonist, were used to characterize the adenosine receptor subtype in the airways of allergic rabbits, respectively. The PC50 (concentration of agonist in mg/ml required to reduce the dynamic compliance 50% from the baseline) values for adenosine, CGS-21680, NECA, and CPA were 9.25 +/- 0.86, 6.8 +/- 0.69, 3.90 +/- 0.27, and 1.45 +/- 0.26 mg/ml, respectively. Thus the potency profile for the bronchoconstrictor of adenosine in this model is a typical A1-receptor subtype (CPA > NECA > CGS-21680 > adenosine). Adenosine also induced further bronchial hyperresponsiveness (BHR) at 1 but not at 24 h following aerosol challenge.(ABSTRACT TRUNCATED AT 250 WORDS)