8-Isoprostane and endothelin-1 as markers of oxidative stress in smokers

ABSTRACT

The aim of this study was to quantify oxidative stress in 40 smokers with chronic obstructive pulmonary disease [COPD], 25 healthy smokers and 20 healthy nonsmokers, as reflected by 8-isoprostane [8-IP] as a marker of lipid peroxidation, protein carbonyl as an index of protein oxidation and endothelin-1 [ET-1] concentrations. This study was also undertaken to determine whether plasma 8-IP, protein carbonyl and ET- 1 status correlated with lung function as assessed by forced expiratory volume in one second [FEV1] and forced vital capacity [FVC] in smokers and in smokers with COPD. Plasma levels of 8-IP and ET-1 were measured by ELISA technique and protein carbonyl was determined by colorimetric method. Antioxidant status, assessed by measuring the glutathione [GSH] and vitamin C levels. Plasma 8-IP, ET-1 and protein oxidation levels were significantly increased in smokers with COPD [45.2 +/- 3.2 pg/ml, 159.6 +/- 9.8 pg/mg protein and 0.55 +/- 0.09 nmol/mg protein respectively] and in healthy smokers [30.6 +/- 2.1 pg/ml, 142 +/- 7.7 pg/mg protein and 0.37 +/- 0.04, nmol/mg protein, respectively] compared with healthy nonsmokers [13.2 +/- 0.92 pg/ml, 72.5 +/- 5.2 pg/mg protein and 0.22 +/- 0.01 nmol/mg protein respectively]. The mean differences of plasma antioxidants, GSH [24.3 +/- 1.61, 28.1 +/- 2.2 and 36.3 +/- 1.93 nmol/mg protein] and vitamin C [1.92 +/- 0.03, 3.17 +/- 0.1 and 5.26 +/- 0.17 mg/L] were significantly decreased in smokers with COPD and healthy smokers compared with healthy nonsmokers, respectively. Significant negative correlations were found between Spirometric data measured as FEV 1% predicted and the plasma levels of 8-IP, ET- 1 and protein oxidation in smokers with COPD, healthy smokers, or healthy nonsmokers. On the other hand, there were significant positive correlations between FEV1% predicted and the levels of plasma vitamin C and GSH in the three studied groups. Conclusions: These data confirm decreased antioxidant capacity [GSH and vitamin C] and increased oxidative stress markers [8-IP, ET- I and protein oxidation] in healthy smokers and smokers with COPD, indicating the presence of systemic oxidative stress. However, relationship was found between plasma oxidant/antioxidant levels and measurements of airflow limitation in either healthy smokers or in smokers with COPD