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To evaluate the potential inhibitory effect of theophylline on the pulmonary oxidative stress in asthma and chronic obstructive pulmonary disease (COPD), we concomitantly measured the blood levels of theophylline, a non-selective phosphodiesterase (PDE) inhibitor and lipid peroxides as an index of oxidative stress. The plasma levels of lipid peroxides were significantly elevated in patients with asthma (3.48 +/- 0.11 nmol ml(-1); mean +/- SEM; n=21, P<0.01), non- or ex-smoking patients with COPD (3.55 +/- 0.11 nmol ml(-1); n = 20, P<0.01), and current-smoking patients with COPD (3.53 +/- 0.15 nmol ml(-1); n = 15, P<0.01), respectively, as compared to those of non-smoking controls (3.02 +/- 0.08 nmol ml(-1); n = 19). There was a significant negative correlation between the plasma level of lipid peroxides and the forced expiratory volume in 1 sec (FEV1)% of forced vital capacity in these subjects (r = -0.304; n = 75, P < 0.01). In asthmatics, there was a significant negative correlation between the plasma level of lipid peroxides and the serum level of theophylline (r = -0.495; n = 18, P<0.05). These results suggest that there may be increased oxidative stress in patients with asthma and COPD, and indicate that oxidative stress could possibly attribute to the pathophysiology of asthma and COPD in leading to airflow obstruction and that theophylline could potentially inhibit oxidative stress in the process of bronchopulmonary inflammation in asthmatics.

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These data suggest that A23187 exposure induced AHR to SP possibly by reducing NO levels in the airway tissues. This may be due to damaged airway epithelium and/or NO breakdown by activated inflammatory cells in the airways of these guinea pigs.