Airway function, oedema, cell infiltration and nitric oxide generation in conscious ozone‐exposed guinea‐pigs: effects of dexamethasone and rolipram

• Published in: British journal of pharmacology Vol. 136; no. 5; pp. 735 - 745
• Main Authors: Toward, Toby J, Broadley, Kenneth J
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.07.2002
• Subjects: Airway hyperreactivity; Animals; corticosteroid; Dexamethasone - pharmacology; Dexamethasone - therapeutic use; Guinea Pigs; leukocytes; lung function; Male; Neutrophil Infiltration - drug effects; Neutrophil Infiltration - physiology; nitric oxide; Nitric Oxide - metabolism; oedema; Oxidative Stress - drug effects; Oxidative Stress - physiology; ozone; Ozone - adverse effects; phosphodiesterase‐4 inhibitor; Pulmonary Disease, Chronic Obstructive - chemically induced; Pulmonary Disease, Chronic Obstructive - drug therapy; Pulmonary Disease, Chronic Obstructive - metabolism; Pulmonary Edema - chemically induced; Pulmonary Edema - drug therapy; Pulmonary Edema - metabolism; Rolipram - pharmacology; Rolipram - therapeutic use
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0704764

The effects of ozone inhalation (90 min, 2.15±0.05 p.p.m.) and their modification by dexamethasone (20 mg kg−1) or the phosphodiesterase‐4 inhibitor, rolipram (1 mg kg−1), administered (i.p.) 24 and 0.5 h before and 24 h after ozone exposure were examined in conscious guinea‐pigs. Ozone caused an early‐phase bronchoconstriction (EPB) as a fall in specific airways conductance (sGaw) measured by whole body plethysmography, followed at 5 h by a late‐phase bronchoconstriction (LPB) and increased respiratory rate. Rolipram did not alter this profile but dexamethasone inhibited the EPB. Airway hyperreactivity to inhaled histamine (1 mM, 20 s) occurred at 0.5, 2, 12, 24 and 48 h after ozone inhalation, the 2 h change being abolished by rolipram and dexamethasone. Bronchoalveolar lavage fluid (BALF) macrophages, eosinophils and neutrophils were significantly (P<0.05) elevated at 12, 24 and 48 h after ozone exposure, the 48 h influx being significantly attenuated (P<0.05) by rolipram and dexamethasone. BALF nitric oxide (NO) metabolites decreased 0.5 h after ozone exposure by 52%, recovered at 2 h and significantly increased at 12 (101%) and 24 h (127%). The elevated NO was unaffected by rolipram or dexamethasone. Lung oedema, measured from wet/dry weight differences, was significant 12, 24 and 48 h after ozone exposure, the latter being significantly attenuated (P<0.05) by rolipram and dexamethasone. Ozone exposure of guinea‐pigs produced features common to COPD. Although rolipram and dexamethasone did not affect the airway function changes, they inhibited the inflammation, airway hyperreactivity and oedema. British Journal of Pharmacology (2002) 136, 735–745; doi:10.1038/sj.bjp.0704764