Oxidative Stress and Antioxidant Status in Saudi Asthmatic Patients

Asthma is a chronic inflammatory airway disorder associated with recruitment of inflammatory cells. It is a common illness which affects an estimated 300 million people of all ages and ethnic backgrounds worldwide with significant costs to the health care system. A significant increase in the prevalence of bronchial asthma has been reported in Saudi children in the Kingdom of Saudi Arabia. An overall increase from 8% to 23% was observed over a period of 9 years (1986 to 1995). The expression of asthma is a complex, interactive process that depends on the interplay between two major factors, host factors and environmental exposures that occur at a crucial time in the development of the immune system. Oxidative stress has been implicated in the pathogenesis of several inflammatory lung disorders. Studies demonstrate an increased oxidative stress in children and adults with asthma in their lungs and in their circulation. Oxidative stress is measured by observing the damage inflicted by reactive oxygen species upon various biomolecules, such as lipids, proteins or DNA. Decreased antioxidant capacity in plasma and bronchoalveolar lavage during stable asthma and in exacerbation, provide further evidence for increased oxidative stress in asthma. Several reports have found alterations in many antioxidant indices in asthma. In this study, the levels of the non-enzymatic antioxidants: reduced glutathione, α-tocopherol and ascorbic acid, as well as the levels of enzymatic antioxidants: superoxide dismutase, glutathione peroxidase were measured in asthmatic patients and controls. Furthermore, total antioxidant status was measured in both groups. The concentration of 8-oxo-deoxyGuanosine (8-oxodG), an oxidative DNA damage marker in the serum of asthmatic patients was also measured. Other oxidative stress biomarkers such as lipid peroxidation product, malondialdehyde (MDA), and nitric oxide metabolites were also measured. The study showed significantly higher MDA level in asthmatics compared to control subjects (22.13 ± 2.006 nmol/hour/ml, 13.86 ± 0.6063 nmol/hour/ml respectively). Similarly, oxidative DNA damage (8-oxodG) (48.91 ± 0.9847 ng/ml, 31.11 ± 1.301 ng/ml respectively) and total nitrites and nitrates (39.21 ± 4.850 μmol/ml, 26.61 ± 2.984 μmol/ml respectively) were higher in asthmatics compared to controls. Moreover, asthmatic patients showed significantly decreased level of reduced glutathione when compared to controls (12.33 ± 0.3121 μg/ml, 20.22 ± 1.187 μg/ml respectively) and non-significant lower level of ascorbic acid (25.30 ± 2.311 μg/ml, 28.80 ± 2.238 μg/ml respectively). Furthermore, Asthmatics showed significantly decreased level of α-tocopherol when compared to controls (39.79 ± 0.86 μmol/l, 54.21 ± 1.25 μmol/l respectively). Glutathione peroxidase level was significantly reduced in asthmatics when compared to controls (0.2803 ± 0.0045 U\ml, 0.3278 ± 0.0035 U\ml respectively). However, the level of superoxide dismutase was significantly higher in asthmatics compared to controls (251.1 ± 2.824U\ml, 189.1 ± 3.822U\ml respectively). In addition to that, total antioxidant status was significantly lower in asthmatics compared to controls (1.155 ± 0.0592 mmol/l, 1.776 ± 0.0689 mmol/l respectively). Asthma is associated with decreased levels of enzymatic, glutathione peroxidase and nonenzymatic antioxidants such as α-tocopherol, ascorbic acid, and reduced glutathione. Moreover, evidence of increased oxidative stress is reflected by the increased oxidative damage markers in asthmatics such as: 8-oxo-dG, total nitrates and nitrites and MDA. The higher superoxide dismutase level observed in asthmatics could be a compensatory response to the increased oxidative stress