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Early and late bronchoconstrictions, airway hyper-reactivity, leucocyte influx and lung histamine and nitric oxide after inhaled antigen: effects of dexamethasone and rolipram

Toward, Toby J. and Broadley, Kenneth John 2004. Early and late bronchoconstrictions, airway hyper-reactivity, leucocyte influx and lung histamine and nitric oxide after inhaled antigen: effects of dexamethasone and rolipram. Clinical and Experimental Allergy 34 (1) , pp. 91-102. 10.1111/j.1365-2222.2004.01833.x

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Background Guinea-pig models can provide the essential features of asthma, including early- (EAR) and late- (LAR) phase asthmatic responses, airway hyper-reactivity (AHR) and inflammatory cell influx; however, these components are rarely demonstrated all in the same model. Objectives The aim of this study was to establish a conscious guinea-pig model with these essential features of asthma and to correlate these with bronchoalveolar lavage fluid (BALF) histamine and nitric oxide (NO) levels. The model would be validated from the susceptibility of these parameters to standard anti-asthmatic agents, the steroid, dexamethasone, and a phosphodiesterase-4 (PDE4) inhibitor, rolipram. Methods Guinea-pigs were sensitized with ovalbumen (OA) (10 μg plus Al2(OH)3 100 mg, intraperitoneal (i.p.)) and 14 days later received inhaled OA (100 μg/mL) or vehicle for 1 h. Airway function was measured by whole-body plethysmography as specific airway conductance (sGaw). Reactivity to inhaled histamine (nose-only, 1 mm, 20 s) was recorded 24 h before and at 6, 12 or 24 h after OA challenge. BALF was obtained to determine the total and differential cell counts, NO and histamine. Results Guinea-pigs challenged with OA showed an EAR as a fall in (sGaw) (−54.9±10.8%), which resolved by 6 h and was followed by an LAR between 7 and 11 h (−30.2±8.8%). No bronchoconstriction to inhaled histamine occurred before OA challenge but at 6, 12 or 24 h afterwards, sGaw fell significantly, indicating AHR. At 1 h after OA, macrophages, eosinophils and neutrophils significantly increased in BALF. Macrophages and eosinophils increased further up to 24 h (3- and 44-fold), but neutrophils declined to control levels. BALF histamine levels increased at 0.25 h after OA challenge and peaked at 6 h. BALF NO levels initially fell (44%) 1 h after OA exposure and then progressively rose above control levels. Dexamethasone (20 mg/kg, i.p.) and rolipram (1 mg/kg, i.p.) administered 24 and 0.5 h before and 6 h after OA challenge inhibited leucocyte influx, AHR and the early deficiency and later excess of NO. Dexamethasone but not rolipram attenuated the LAR. Conclusions This model displays many of the features of human asthma with predictable responses to dexamethasone and evidence of anti-asthmatic activity by the PDE4 inhibitor, rolipram.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Pharmacy
Subjects: R Medicine > RM Therapeutics. Pharmacology
R Medicine > RS Pharmacy and materia medica
Uncontrolled Keywords: airway hyper-reactivity; allergen; dexamethasone; guinea-pig airways; histamine; lung lavage; nitric oxide; rolipram
Publisher: Wiley-Blackwell
ISSN: 0954-7894
Last Modified: 04 Jun 2017 03:01

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