Alteration in systemic markers of oxidative and antioxidative status in Tunisian patients with asthma: relationships with clinical severity and airflow limitation

Objective: This study aims to determine the systemic oxidant-antioxidant status in Tunisian patients with asthma. Methods: We evaluated the levels of malondialdehyde (MDA) as thiobarbituric acid complexes, total protein carbonyls (PCs) and advanced oxidation protein products (AOPP). The levels of total thiols, protein sulfhydryls, glutathione (GSH), together with hydrogen peroxide, ascorbic acid, iron and total antioxidant status (TAS) were colorimetrically estimated. Glutathione peroxidase (GSH-Px), catalase (CAT) and superoxide dismutase (SOD) activities were assessed in plasma and erythrocytes by spectrophotometry. We also determined the levels of nitric oxide (NO) and peroxynitrite in plasma from asthmatic patients and healthy controls. The volume of fractionated exhaled NO (Fe-NO) was evaluated by the Medisoft HypAir method. Estimation of DNA damage was determined using the comet assay. Results: Asthmatic patients showed increased levels of MDA in comparison to healthy controls (p<0.001), while no significant difference was found in protein carbonyls (p=0.79) and AOPP (p=0.98). Patients with asthma also had significantly lower levels of total thiols (355.9 +/- 15.72 versus 667.9 +/- 22.65, p<0.001), protein sulfhydryls (333.99 +/- 16.41 versus 591.95 +/- 24.28, p<0.001) and glutathione (p<0.001). They also showed decreased GSH-Px activity (p<0.001), whereas no significant differences in measurements of catalase and SOD enzyme activities were observed between the two groups (respectively, p=0.06 and p=0.55). In addition, ascorbic acid and nitric oxide levels were decreased in asthmatics in comparison to controls (p<0.01). Conclusions: Our findings highlight that oxidative stress and defective anti-oxidative status are major alterations in Tunisian patients with asthma.