Biological activity of leukotriene B4 analogs: inhibition of guinea pig eosinophil migration in vitro by the 2,6-disubstituted pyridine analogs U-75,302 and U-75,485.

A "late phase" antigen-induced bronchoalveolar eosinophilia has been demonstrated in ovalbumin sensitized guinea pigs (1,2). This in vivo response to antigen inhalation can be inhibited by a 2,6-disubstituted pyridine analog of LTB4, U-75,302(2) (3). In the present study, the mechanism of the drug action was studied by assessing the activity of U-75,302 and a second analog, U-75,485 to displace [3H]-leukotriene B4 binding at the guinea pig eosinophil membrane, as well as their action as chemoattractants or inhibitors of the directional migration of guinea pig eosinophils in vitro. Radioligand competition experiments demonstrated that both analogs interacted strongly with the high affinity LTB4 binding sites on guinea pig eosinophil membrane. Both analogs are powerful chemoattractants for guinea pig eosinophils since they induced directional migration of guinea pig eosinophils when administered alone. In addition, when the cells were treated with either analog and their chemotaxis response was measured in response to a natural chemoattractant, both U-75,302 and U-75,485 at concentrations of 0.1 to 100 microM dose dependently inhibited the LTB4 induced chemotaxis response. The EC50s obtained for U-75,302 and U-75,485 as inhibitors of LTB4 induced guinea pig eosinophil chemotaxis were estimated to be 11.5 +/- 5.5 microM and 5.4 +/- 2.5 microM respectively. Under the same conditions, they had no significant effect upon eosinophil migration induced by zymosan activated plasma at concentrations below 100 microM. We suggest that the inhibition of antigen-induced eosinophil infiltration in guinea pig airway in vivo by U-75,302 or U-75,485 may be a result of partial antagonism or desensitization at the LTB4 receptor level of guinea pig eosinophils.     

Effect of a peptide leukotriene antagonist, ONO-1078 on antigen-induced airway microvascular leakage in actively sensitized guinea pigs.

We examined the effect of ONO-1078, a peptide leukotriene antagonist, on antigen-induced airway microvascular leakage in ovalbumin-sensitized guinea pigs. When guinea pigs were pretreated with mepyramine, ovalbumin challenge increased vascular permeability to Evans blue dye in trachea, main bronchi and intrapulmonary airways. Oral administration of ONO-1078 significantly reduced microvascular leakage in intrapulmonary airways at doses more than 3 mg/kg, but not in trachea. Moreover, oral administration of ONO-1078 significantly reduced SRS-A mediated microvascular leakage into all airway tissues and was more effective in intrapulmonary airways at 3 mg/kg. Simultaneously, ONO-1078 also inhibited SRS-A mediated bronchoconstriction. On the other hand, azelastine (10 mg/kg, p.o.), an anti-asthma agent, failed to inhibit microvascular leakage into the airways. These results suggest that peptide leukotrienes may be important mediators of airway microvascular leakage, and that the inhibitory effect of ONO-1078 on antigen-induced airway microvascular leakage in addition to the blockade of bronchoconstriction may have therapeutic implications for bronchial asthma.     

In vivo PAF-induced airway eosinophil accumulation reduces bronchial responsiveness to inhaled histamine

Chronic eosinophilic bronchitis and bronchial hyperresponsiveness have been considered to be the fundamental features of bronchial asthma. However, the role of airway eosinophils in bronchial responsiveness in vivo has not been fully discussed. The aim of this study was to investigate the direct effect of airway eosinophil accumulation on bronchial responsiveness in vivo. Guinea pigs were transnasally treated with platelet activating factor (PAF) or vehicle twice a week for a total of 3 weeks. Anesthetized guinea pigs were surgically cannulated and artificially ventilated 48 h after the last administration of PAF or vehicle. Ten minutes after the installation of artificial ventilation, ascending doses of histamine were inhaled. In a subsequent study, selective inhibitors of diamine oxidase and histamine N-methyltransferase were intravenously administered before the histamine inhalation in the PAF-treated animals. Next study was conducted 20 min after treatment with indomethacin in this study line. Finally, ascending doses of methacholine were inhaled in our animal model. Proportion of eosinophils and the number of nuclear segmentation in bronchoalveolar lavage fluid significantly increased in guinea pigs treated with PAF compared with vehicle and this finding was confirmed histologically. Nevertheless, bronchial responsiveness to inhaled histamine, but not methacholine, was significantly decreased by the PAF treatment. This bronchoprotective effect induced by PAF remained following aminoguanidine and histamine N-methyltransferase administration, but abolished by treatment of indomethacin. These results suggest that in vivo airway eosinophils may reduce nonspecific bronchial responsiveness through production of inhibitory or bronchoprotective prostanoids, but not through histaminase production.     

No involvement of lipid mediators in a guinea pig model of ultrasonically nebulized distilled water-induced bronchoconstriction

An inhalation of ultrasonically nebulized distilled water (UNDW) induces bronchoconstriction only in asthmatics, but the mechanism underlying the response is not fully understood. We have reported that bronchoconstriction occurs immediately after UNDW is inhaled 20 min after an antigen challenge in guinea pigs. Our aim was to examine the role of lipid mediators in this response. Passively sensitized guinea pigs were anesthetized and artificially ventilated. A sulfidopeptide leukotriene receptor antagonist, KCA-757, and platelet-activating factor antagonists, Y-24180 and E6123, were administered i.v. 15 min after an aerosolized antigen challenge, and UNDW was inhaled 5 min later. KCA-757, Y-24180, or E6123 did not, significantly alter the UNDW-induced bronchoconstriction. Together with our previous data that thromboxane A2 receptor antagonists did not influence the UNDW-induced bronchoconstriction, the present results suggest that lipid mediators are not involved in the UNDW-induced bronchoconstriction in our guinea pig model.     

Role of tachykinins in hyperpnea-induced bronchovascular hyperpermeability in guinea pigs

Isocapnic dry gas hyperpnea causes bronchoconstriction in guinea pigs that is mediated by release of tachykinins from airway sensory nerves. Exogenous neuropeptides can induce microvascular leak. Therefore we tested whether dry gas hyperpnea also elicits bronchovascular hyperpermeability by measuring Evans blue-labeled albumin extravasation along the airways of mechanically ventilated guinea pigs. We found that 1) room temperature dry gas hyperpnea increased Evans blue extravasation in extrapulmonary and intrapulmonary airways as a specific consequence of local airway heat/water losses, 2) capsaicin pretreatment ablated the bronchoconstrictor response to dry gas hyperpnea and reduced bronchovascular leak only in intrapulmonary airways, 3) phosphoramidon given to capsaicin-pretreated animals partially restored dry gas hyperpnea-induced bronchoconstriction and increased the vascular hyperpermeability response to hyperpnea in intrapulmonary airways, and 4) propranolol administration had no important effects on any of these airway responses. We conclude that dry gas hyperpnea causes bronchovascular hyperpermeability in guinea pigs. Tachykinins have a dominant role in this response in the intrapulmonary airways, although another mechanism may also contribute to the microvascular leak in the extrapulmonary airways.     

Inhibition of antigen-induced airway hyperresponsiveness, but not acute hypoxia nor airway eosinophilia, by an antagonist of platelet-activating factor

The role of platelet-activating factor (PAF) in Ag-induced airway hyperresponsiveness was evaluated in a guinea pig model using the PAF antagonist SDZ 64-412. Repeated OVA challenge by aerosol (twice weekly x 4 wk) of previously sensitized guinea pigs produced striking airway hyperresponsiveness as determined by pulmonary resistance changes to increasing doses of inhaled acetylcholine given 3 days after the last OVA challenge. Each OVA challenge produced significant hypoxia that was unaffected by oral pretreatment with 20 mg/kg SDZ 64-412, 2 h before each challenge (pO2 = 35 +/- 2 mm Hg for OVA alone vs 40 +/- 6 mm Hg for SDZ and OVA groups, respectively). SDZ 64-412 pretreatment abolished the airway hyperresponsiveness resulting from repeated Ag challenge. Morphometric analysis revealed that SDZ 64-412 treatment had no effect on the increased numbers of eosinophils that infiltrated the airways of OVA-challenged guinea pigs. These results suggest that PAF may be a primary mediator of airway hyperresponsiveness, but not acute bronchoconstriction, induced by repeated Ag challenge. This activity of PAF appears independent of eosinophil recruitment to airways.     

OKY-046 inhibits anaphylactic bronchoconstriction and reduces histamine level in bronchoalveolar lavage fluid in sensitized guinea pigs.

We investigated the effects of OKY-046, a potent and selective thromboxane A2 (TxA2) synthetase inhibitor, on anaphylactic bronchoconstriction and release of chemical mediators into airway lumen in sensitized guinea pigs in vivo. OKY-046 dose-dependently inhibited antigen-induced anaphylactic bronchoconstriction with or without mepyramine, a histamine H1 antagonist. In the presence of mepyramine, OKY-046 (300 mg/kg, p.o.) elicited significant reductions in histamine (1 min) and TxB2 increases (1-15 min) in bronchoalveolar lavage (BAL) fluid but significantly increased the plasma level of 6-keto-PGF1 alpha, a stable PGI2 metabolite, after antigen challenge. On the contrary, indomethacin only significantly reduced increases in TxB2 levels. These results suggest that the antiasthmatic effect of OKY-046 is probably due to inhibition of TxA2 synthesis and suppression of histamine release via a PGI2 shunting mechanism.     

Atropine pretreatment enhances airway hyperreactivity in antigen-challenged guinea pigs through an eosinophil-dependent mechanism

Airway hyperreactivity in antigen-challenged animals is mediated by eosinophil major basic protein (MBP) that blocks inhibitory M(2) muscarinic receptors on parasympathetic nerves, increasing acetylcholine release onto M(3) muscarinic receptors on airway smooth muscle. Acutely, anticholinergics block hyperreactivity in antigen-challenged animals and reverse asthma exacerbations in the human, but are less effective in chronic asthma. We tested whether atropine, given before antigen challenge, affected hyperreactivity, M(2) receptor function, eosinophil accumulation, and activation. Sensitized guinea pigs received atropine (1 mg/kg ip) 1 h before challenge and 6 h later. Twenty-four hours after challenge, animals were anesthetized, vagotomized, paralyzed, and ventilated. Airway reactivity to electrical stimulation of the vagi and to intravenous acetylcholine was not altered by atropine pretreatment in nonsensitized animals, indicating that atropine was no longer blocking postjunctional muscarinic receptors. Antigen challenge induced airway hyperreactivity to vagal stimulation that was significantly potentiated by atropine pretreatment. Bronchoconstriction induced by acetylcholine was not changed by antigen challenge or by atropine pretreatment. M(2) receptor function was lost in challenged animals but protected by atropine pretreatment. Eosinophils in bronchoalveolar lavage and within airway tissues were significantly increased by challenge but significantly reduced by atropine pretreatment. However, extracellular MBP in challenged airways was significantly increased by atropine pretreatment, which may account for reduced eosinophils. Depleting eosinophils with antibody to IL-5 before challenge prevented hyperreactivity and significantly reduced MBP in airways of atropine-pretreated animals. Thus atropine pretreatment potentiated airway hyperreactivity by increasing eosinophil activation and degranulation. These data suggest that anticholinergics enhance eosinophil interactions with airway nerves.     

Inhibition of airway hyperreactivity, edema, and lung cell infiltration by compound U-83836E in sensitized guinea pigs

Sensitized guinea pigs were used to assess the effect of treatment with the compound U-83836E ((-)-2-[[4-(2,6-di-1-pyrrolidinyl-4-pyrimidinyl)-1-piperazinyl]methyl]-3 ,4-dihydro-2,5,7,8-tetramethyl-2H--benzopyran-6-ol, dihydrochloride) on the antigen-induced late-phase (16 h) airway hyperreactivity, increase in inflammatory cell number, edema, and release of inflammatory mediators in the bronchoalveolar lavage (BAL) fluid. After antigen challenge, an increase of the in vitro reactivity of the trachea and upper bronchi to acetylcholine and histamine and an increase in the number of leukocytes in the BAL fluid, mainly eosinophils and mononuclear cells, were observed. The concentrations of proteins, histamine, and PGE2 in the BAL fluid were also significantly increased by 53, 57, and 216%, respectively, after antigen challenge. Treatment with U-83836E (10 mg/kg) given i.p. 17 and 3 h before and 6 h after antigen challenge inhibited by approximately 80% the total cell number in the airways and the BAL fluid protein content. Moreover, this treatment totally inhibited airway hyperreactivity. Histamine and PGE2 levels in the BAL fluid were not significantly affected by U-83836E treatment. These results indicate that U-83836E is effective against some of the characteristic features of asthma in ovalbumin-sensitized guinea pigs.     

Ozone-induced hyperresponsiveness and blockade of M2 muscarinic receptors by eosinophil major basic protein.

Control of airway smooth muscle is provided by parasympathetic nerves that release acetylcholine onto M(3) muscarinic receptors. Acetylcholine release is limited by inhibitory M(2) muscarinic receptors. In antigen-challenged guinea pigs, hyperresponsiveness is due to blockade of neuronal M(2) receptors by eosinophil major basic protein (MBP). Because exposure of guinea pigs to ozone also causes M(2) dysfunction and airway hyperresponsiveness, the role of eosinophils in ozone-induced hyperresponsiveness was tested. Animals were exposed to filtered air or to 2 parts/million ozone for 4 h. Twenty-four hours later, the muscarinic agonist pilocarpine no longer inhibited vagally induced bronchoconstriction in ozone-exposed animals, indicating M(2) dysfunction. M(2) receptor function in ozone-exposed animals was protected by depletion of eosinophils with antibody to interleukin-5 and by pretreatment with antibody to guinea pig MBP. M(2) function was acutely restored by removal of MBP with heparin. Ozone-induced hyperreactivity was also prevented by antibody to MBP and was reversed by heparin. These data show that loss of neuronal M(2) receptor function after ozone is due to release of eosinophil MBP.     

Antigen inhalation induces mast cells and eosinophils infiltration in the guinea pig esophageal epithelium involving histamine-mediated pathway

Antigen challenge in sensitized guinea pig esophagus in vitro induces mast cell degranulation and histamine release. This study tests the hypothesis that antigen inhalation in vivo induces infiltration of the esophageal epithelium by mast cells and eosinophils via a histamine pathway. Actively sensitized guinea pigs were exposed to inhaled 0.1% ovalbumin. One or 24 h after inhalation exposure, the esophagus was processed for immunofluorescent staining of mast cell tryptase and eosinophil major basic protein (MBP). Additional animals were pretreated with thioperamide, a histamine H4/H3 receptor antagonist. Total tryptase- and MBP-labeled cells and percent of positive cells in the epithelial layer were counted. The total number of mast cells was unchanged after inhalation challenge, but the percentage in the epithelium increased 1 h after challenge. The total number of eosinophils increased 1 h after challenge, and the percentage migrating to the epithelium increased by 24 h after challenge. Mast cell migration into the mucosal epithelium preceded that of eosinophils. Thioperamide inhibited mast cell and eosinophil migration. In conclusion, antigen inhalation in sensitized animals induces mast cells and eosinophils to infiltrate in the esophageal epithelium via histamine-mediated mechanism.     

Lack of adrenomedullin on antigen-induced bronchoconstriction in guinea pigs in vivo

Antigen challenge can provoke acute bronchoconstriction, recognized as immediate asthmatic response (IAR), but the evolving events in this reaction are not well defined. Recently, a novel peptide, designated adrenomedullin, was isolated from human pheochromocytoma, and has been shown to have potent systemic and pulmonary vasodilator activity.The purpose of this study was to elucidate the influence of adrenomedullin in the development of IAR. Passively sensitized guinea pigs were anesthetized and treated with diphenhydramine hydrochloride, and then artificially ventilated. Ovalbumin was inhaled after an intravenous administration of adrenomedullin. Other studies were performed in naive guinea pigs to investigate the airway responses to inhaled methacholine or histamine after an intravenous administration of adrenomedullin. Antigen challenge caused bronchoconstriction in sensitized guinea pigs. Adrenomedullin did not inhibit the antigen-induced bronchoconstriction in sensitized guinea pigs or the dose-dependent responses to inhaled methacholine or histamine in naive animals in spite of its vasodilating effect. We conclude that an intravenous administration of adrenomedullin does not influence antigen-induced bronchoconstriction or bronchial responsiveness to inhaled methacholine or histamine in vivo.     

Repeated antigen inhalation results in a prolonged airway eosinophilia and airway hyperresponsiveness in primates

The effects of repeated antigen inhalation on airway cellular composition and airway responsiveness were examined in primates. Airway cellular composition was assessed by bronchoalveolar lavage (BAL), and airway responsiveness was measured as the bronchoconstrictor response to cumulative methacholine dose-response determinations over the course of a 10-wk study. Control animals, exposed to repeated vehicle inhalation challenges, were tested in parallel with the antigen-challenged group. Repeated antigen inhalation resulted in a prolonged inflammatory reaction characterized by a large increase in airway eosinophils (3 +/- 1 to 59 +/- 15%, P less than 0.01). Airway eosinophilia was associated with an increase in airway responsiveness as indicated by a leftward shift in the methacholine dose-response curves, an increase in the slope of the dose-response curves, and a decrease in PC100 values (the dose of methacholine required to cause a 100% increase in lung resistance). The number of BAL eosinophils and the level of eosinophil major basic protein in BAL correlated significantly with methacholine PC100 values (r = 0.61, P less than 0.01 and r = 0.64, P less than 0.01, respectively). Histological examination of lung biopsy samples taken at week 10 of the study demonstrated a striking infiltration of eosinophils in the antigen-challenged animals. These results support earlier observations that demonstrated an association between increases in airway eosinophils and increases in airway responsiveness and suggest that eosinophils are involved in the pathogenesis of hyperresponsive airways.     

The effect of a novel leukotriene C4/D4 antagonist, BAY-x-7195, on experimental allergic reaction

The effects of a novel leukotriene (LT) C₄/D₄ antagonist, BAY-x-7195 on experimental allergic reactions in airway and skin were compared to that of ONO-1078. BAY-x-7195 showed an antagonistic action to LTD₄-induced bronchoconstriction in vitro and in vivo. In in vitro experiments, BAY-x-7195 inhibited LTD₄-induced contraction of isolated guinea pig tracheal muscle (pA2=8.03). BAY-x-7195 at doses of 3 – 30 mg/kg clearly inhibited LTD₄-induced increases in respiratory resistance (Rrs) in guinea pigs. In contrast, BAY-x-7195 inhibited significantly U-46619-induced increases in Rrs at a dose of 30 mg/kg in guinea pigs. BAY-x-7195 at doses of 3 — 30 mg/kg inhibited the aerosolized antigen-induced biphasic increase in Rrs in guinea pigs. Moreover BAY-x-7195 inhibited repeated aeroantigen-induced airway hyperreactivity in guinea pigs. In mice, aeroantigen-induced airway inflammation were clearly inhibited by BAY-x-7195. These results show the efficacy of BAY-x-7195 against the antigen-induced increase in airway resistance and antigen-induced airway hyperreactivity in guinea pigs and mice, probably due to anti-LTD₄ antagonistic action and the inhibition of antigen-induced airway inflammation.     

Blockade of JAK2 by tyrphostin AG-490 inhibits antigen-induced eosinophil recruitment into the mouse airways

We studied the effect of tyrphostin AG-490, a specific Janus kinase 2 (JAK2) inhibitor, on antigen-induced eosinophil recruitment into the airways of sensitized mice and on IL-5-induced chemokinesis and adhesiveness of eosinophils. The in vivo administration of AG-490 prevented antigen-induced eosinophil infiltration in the airways of sensitized mice in a dose-dependent manner. However, the administration of AG-490 did not affect antigen-induced IL-5 production in the airways nor in vitro antigen-induced IL-5 production and T cell proliferation of spleen cells. Furthermore, AG-490 inhibited IL-5-induced chemokinesis and beta1-integrin adhesiveness of eosinophils in vitro. Because antigen-induced eosinophil recruitment into the airways is mediated by IL-5, these results indicate that JAK2 activation is critical for antigen-induced, IL-5-dependent mobilization of eosinophils into the tissue.     

Effect of a novel 5-lipoxygenase inhibitor, E6080 on bronchospasm, airway cellular infiltration and leukotriene production in guinea pigs.

6-Hydroxy-2-(4-sulfamoylbenzylamino)-4,5,7-trimethylbenzothiazo le hydrochloride (E6080), an orally active and selective 5-lipoxygenase inhibitor, dose-dependently inhibited the bronchospasm induced by antigen (ovalbumin) inhalation in sensitized conscious guinea pigs. The inhibitory effect of E6080 was more potent than that of a typical 5-lipoxygenase inhibitor, AA861, but less than that of a leukotriene (LT) antagonist, LY171883. When airway infiltration of neutrophils and eosinophils was measured in bronchoalveolar lavage fluid (BALF) at 6 h after antigen inhalation by passively sensitized guinea pigs, the inhibitory effect of E6080 on neutrophil infiltration was more marked than that on eosinophil infiltration. The inhibitory effect of E6080 on bronchoalveolar cellular infiltration and bronchoepithelial damage was confirmed by examination of photomicrographs of the lung. In addition to the above pharmacological effects, E6080 inhibited the increase in BALF levels of both i-LTC4 and i-LTB4. These results suggest that E6080 may prove to be effective for the treatment of asthma, in which large amounts of leukotrienes (LTs) are elaborated.     

Neurokinins and inflammatory cell iNOS expression in guinea pigs with chronic allergic airway inflammation

In the present study we evaluated the role of neurokinins in the modulation of inducible nitric oxide synthase (iNOS) inflammatory cell expression in guinea pigs with chronic allergic airway inflammation. In addition, we studied the acute effects of nitric oxide inhibition on this response. Animals were anesthetized and pretreated with capsaicin (50 mg/kg sc) or vehicle 10 days before receiving aerosolized ovalbumin or normal saline twice weekly for 4 wk. Animals were then anesthetized, mechanically ventilated, given normal saline or N(G)-nitro-l-arginine methyl ester (l-NAME, 50 mg/kg ic), and challenged with ovalbumin. Prechallenge exhaled NO increased in ovalbumin-exposed guinea pigs (P < 0.05 compared with controls), and capsaicin reduced this response (P < 0.001). Compared with animals inhaled with normal saline, ovalbumin-exposed animals presented increases in respiratory system resistance and elastance and numbers of total mononuclear cells and eosinophils, including those expressing iNOS (P < 0.001). Capsaicin reduced all these responses (P < 0.05) except for iNOS expression in eosinophils. Treatment with l-NAME increased postantigen challenge elastance and restored both resistance and elastance previously attenuated by capsaicin treatment. Isolated l-NAME administration also reduced total eosinophils and mononuclear cells, as well as those cells expressing iNOS (P < 0.05 compared with ovalbumin alone). Because l-NAME treatment restored lung mechanical alterations previously attenuated by capsaicin, NO and neurokinins may interact in controlling airway tone. In this experimental model, NO and neurokinins modulate eosinophil and lymphocyte infiltration in the airways.     

CLA reduces antigen-induced histamine and PGE(2) release from sensitized guinea pig tracheae

Conjugated linoleic acid (CLA) has been shown to enhance immune reactions such as lymphocyte blastogenesis and delayed-type hypersensitivity. We investigated the role of CLA in type I (immediate) hypersensitivity, using a guinea pig tracheal superfusion model for measuring antigen-induced airway smooth muscle contraction and inflammatory mediator release. Female Hartley guinea pigs were fed a diet supplemented with 0.25 g corn oil or linoleic acid/100 g of diet (control) or 0.25 g CLA/100 g of diet for at least 1 wk before and during active sensitization to ovalbumin antigen. Tracheae from sensitized guinea pigs were suspended in air-filled water-jacketed (37 degrees C) tissue chambers in a superfusion apparatus. Tracheae were superfused with buffer containing antigen, and tissue contraction was recorded. Superfusate was collected at 90-s intervals for evaluation of histamine and PGE(2) release. CLA did not affect antigen-induced tracheal contractions when expressed as gram contraction per gram tissue. CLA significantly reduced antigen-induced histamine and PGE(2) release. CLA appears to decrease release of some inflammatory mediators during type I hypersensitivity reactions.     

Angiostrongylus cantonensis: role of eosinophils in the neurotoxic syndrome (Gordon-like phenomenon)

The role of eosinophils in the pathophysiology of Angiostrongylus cantonensis infections was investigated in nonpermissive (guinea pig) and permissive (rat) hosts. Neurological symptoms similar to the Gordon phenomenon (ataxia, tremor, paralysis) together with a loss of Purkinje cells in the cerebellum were observed after intracraneal injection of human eosinophil extracts or after infection with A. cantonensis, only in guinea pigs and not in rats. Blood eosinophilia as well as eosinophil numbers present in the cerebellum and in the cerebrospinal fluid were higher in guinea pigs than in rats, at all times after infection with A. cantonensis. Increased levels of cytotoxicity toward L3 larvae in vitro were obtained in the presence of guinea pig eosinophils and IgE antibodies, rather than with the corresponding rat effector system. The detection of one eosinophil granule component, the eosinophil peroxidase, in the cerebrospinal fluid from infected guinea pigs but not from rats suggested that in nonpermissive hosts, neurological disorders, similar to the previously described Gordon phenomenon, might be due to eosinophil neurotoxins released after interaction of eosinophils with the parasites.     

Effects of antisense oligodeoxynucleotides targeting CCR3 on the airway response to antigen in rats

Asthma is characterized by airway hyperresponsiveness (AHR) and inflammation, consisting predominantly of eosinophils within the airway lumen and walls. Eosinophil recruitment to the airways is mediated mainly by eotaxin and other chemokines that bind to the CC-chemokine receptor-3 (CCR3), which is highly expressed on eosinophils. This study assessed whether topical inhibition of CCR3 mRNA expression by phosphorothioate antisense oligodeoxynucleotides (AS-ODNs) modifies pulmonary eosinophilia and AHR in an antigen-induced allergic asthma model in Brown Norway (BN) rats. Results show that specific inhibition of CCR3 expression in the lungs by an AS-ODN (AS4) reduced total eosinophil infiltration and the percentage of eosinophils into the airways of ovalbumin challenged rats. Moreover, reduction in CCR3 mRNA levels was correlated with a decrease in CCR3 protein in lung tissue. In addition, AS4 treatment had no effect on circulating eosinophils or on eosinophils in the bone marrow. Finally, AHR was significantly decreased in AS4-treated rats when compared with rats treated with a mismatch AS-ODN. In conclusion, inhibition of the expression of CCR3 decreased pulmonary eosinophilia and reduced AHR after antigen challenge in rats. Topical inhibition of CCR3 expression, using an AS-ODN, could represent a novel approach for the treatment of asthma.