l-663536 and Eosinophilia

Subcutaneous heat-coagulated egg white implants (EWI) induce chronic, intense local eosinophilia in mice, followed by asthma-like responses to airway ovalbumin challenge. Our goal was to define the mechanisms of selective eosinophil accumulation in the EWI model. EWI carriers were challenged i.p. with ovalbumin and the contributions of cellular immunity and inflammatory mediators to the resulting leukocyte accumulation were defined through cell transfer and pharmacological inhibition protocols. Eosinophil recruitment required Major Histocompatibility Complex Class II expression, and was abolished by the leukotriene B4 (LTB4) receptor antagonist CP 105.696, the 5-lipoxygenase inhibitor BWA4C and the 5-lipoxygenase activating protein inhibitor MK886. Eosinophil recruitment in EWI carriers followed transfer of: a) CD4+ (but not CD4-) cells, harvested from EWI donors and restimulated ex vivo; b) their cell-free supernatants, containing LTB4. Restimulation in the presence of MK886 was ineffective. CC chemokine receptor ligand (CCL)5 and CCL2 were induced by ovalbumin challenge in vivo. mRNA for CCL17 and CCL11 was induced in ovalbumin-restimulated CD4+ cells ex vivo. MK886 blocked induction of CCL17. Pretreatment of EWI carriers with MK886 eliminated the effectiveness of exogenously administered CCL11, CCL2 and CCL5. In conclusion, chemokine-producing, ovalbumin-restimulated CD4+ cells initiate eosinophil recruitment which is strictly dependent on LTB4 production.

Topics: Allergens; Animals; CD4-Positive T-Lymphocytes; Cell Movement; Chemokines; Chronic Disease; Dexamethasone; Eosinophilia; Eosinophils; Indoles; Inflammation; Leukotriene B4; Male; Mice; Mice, Inbred BALB C; Ovalbumin

Experimental toxocariasis was used as a model of eosinophil migration. Mice inoculated with 200 Toxocara canis eggs were treated with the leukotriene inhibitor MK886 (1 mg/kg/day). Eosinophils were counted in peripheral blood (PB), peritoneal cavity (PC) and bronchoalveolar lavage fluid (BALF) samples on post-infection days 3, 6, 12, 18, 24 and 36. Eosinophil expression of Mac-1 and VLA-4 was analysed in PB and PC samples. We found that T. canis infection induced systemic eosinophilia from post-infection day 3, peaking on days 6, 12 and 24 in PB, PC and BALF samples respectively. Eosinophilia was more pronounced in PB and PC samples than in BALF samples, and MK886 downregulated eosinophilia to varying degrees in the different sample types. In PB and PC samples, T. canis infection caused early upregulation of Mac-1 with late changes in the VLA-4 profile, whereas MK886 had opposite effects. The distinct time-dependent eosinophilia peaks and differential involvement of leukotrienes in integrin expression demonstrate that, despite the systemic eosinophilia triggered by T. canis infection, inflammatory responses vary by compartment.

Topics: Animals; Bronchoalveolar Lavage Fluid; Cell Movement; Eosinophilia; Eosinophils; Female; Flow Cytometry; Indoles; Integrin alpha4beta1; Lipoxygenase Inhibitors; Macrophage-1 Antigen; Mice; Mice, Inbred BALB C; Phenotype; Toxocariasis

The involvement of leukotrienes (LTs) in antigen-induced airway hyper-reactivity (AHR) was characterized pharmacologically by using several 5-lipoxygenase (5-LO) inhibitors and LTD4 antagonists in guinea pigs. AHR was evidenced by consistent and significant increases in sensitivity to bronchoconstriction induced by i.v. methacholine in anesthetized and ventilated animals 24 hr after a single ovalbumin aerosol challenge, but maximum methacholine-induced bronchoconstriction did not increase. Animals were pretreated with maximum doses of WY-50,295 tromethamine (WY-50,295), LY-171,883, MK-886 or zileuton, based upon inhibition of antigen-induced LT-dependent bronchoconstriction. WY-50,295, having a long duration of action, was the only compound that prevented AHR when given once before antigen challenge. However, LY-171,883 and MK-886 prevented AHR when a second dose was given 4 hr after challenge. Zileuton, having a short duration of action, failed to prevent AHR when given before and after challenge. The prevention of AHR did not result from functional antagonism (bronchodilation) by any compound. In bronchoalveolar lavage studies, neither WY-50,295 nor MK-886 inhibited the influx of eosinophils into the airways 24 hr after antigen challenge. The results provide pharmacological evidence that LTs play an important role in the pathogenesis of antigen-induced AHR in guinea pigs. Furthermore, the effectiveness of 5-LO inhibitors and LTD4 antagonists in this model depends upon a long duration of drug action and appears to result from inhibition of a direct airway effect of LTs rather than inhibition of eosinophil influx into the airways.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acetophenones; Animals; Antigens; Bronchoconstriction; Eosinophilia; Guinea Pigs; Hydroxyurea; Indoles; Leukotriene D4; Leukotrienes; Lipoxygenase Inhibitors; Male; Naphthaleneacetic Acids; Quinolines; Tetrazoles

1. Repeated aerosolization of leukotriene C4 (LTC4) to guinea-pigs produced leftward shift in their pulmonary resistance (RL) dose-response curves to inhaled acetylcholine (ACh) without increasing the maximum responses. 2. Repeated LTC4 aerosolization did not increase airway eosinophils. 3. The 5-lipoxygenase-activating protein (FLAP) inhibitor, MK-886, prevented the leftward shift in RL dose-response curves to ACh following repeated antigen challenge in guinea-pigs. 4. MK-886 did not inhibit the increased maximal RL produced by repeated antigen challenge, nor inhibit the airway eosinophilia induced by repeated antigen challenge. 5. Our findings suggest that leukotrienes may account for the leftward shift in pulmonary resistance responses caused by antigen but do not cause the airway eosinophilia nor enhanced maximum broncho-constrictor response to antigen.

Topics: 5-Lipoxygenase-Activating Proteins; Administration, Inhalation; Airway Resistance; Animals; Antigens; Asthma; Bronchial Hyperreactivity; Carrier Proteins; Dose-Response Relationship, Drug; Eosinophilia; Guinea Pigs; Indoles; Leukotriene Antagonists; Leukotrienes; Male; Membrane Proteins; Ovalbumin; SRS-A