Association Between Cigarette Smoking and Oxidized Proteins

Abstract

P-159 Introduction: Cigarette smoking is a major source of oxidative stress. Protein carbonyls have been used as a biomarker of oxidative stress because of the relative stability of carbonylated proteins and the high protein concentration in blood. Increased levels of carbonyl groups have been found in serum proteins of smokers compared to nonsmokers. However, the dose effect of cigarette smoke on oxidative stress has not been studied. Hence, we used an ELISA (Enzyme-Linked Immunosorbent Assay) to evaluate plasma protein carbonyls as a parameter of oxidative stress in subjects who were enrolled in the EMphysema and Lung Cancer Action Project (EMCAP). Methods: The EMCAP lung cancer screening program enrolled current and former smokers age 60 years and over without a prior cancer diagnosis. A total of 542 participants (282 males and 260 females) completed a baseline questionnaire and provided blood samples for the biomarker study. The protein oxidation was measured by derivatization of the carbonyl groups with 2,4-dinitrophenylhydrazine (DNPH) and ELISA quantitation of the DNPH group. Results: The mean (± SD) protein carbonyl level was 17.9 ± 2.9 nmol carbonyls/ml plasma. Protein carbonyls did not differ significantly by gender. Carbonyl levels were higher among current than former smokers, but these differences did not attain statistical significance, nor did differences by pack-years, pack/day among current smokers, and smoking duration. In a multiple regression analysis, higher protein carbonyl levels were independently associated with increasing age (5.6 nmol/ml increase per 10 years, 95% CI 1.1, 10.1, p = 0.01), African-American vs. white race/ethnicity, (1.2 nmol/ml, 95% CI 0.2, 2.2, p = 0.01), lower educational attainment (0.7 nmol/ml, 95% CI 0.4, 1.3, p = 0.043) and higher body mass index (0.7 nmol/ml, 95% CI 0.01, 1.4, p = 0.04). Conclusions: Although we found no association between cigarette smoking and protein carbonyls in this older group of long term smokers and exsmokers, associations were found for age, ethnicity, educational attainment and obesity. The measurement of plasma carbonyls by this ELISA technique is relatively easy and suitable for studies on the oxidative stress-related disease. Funding: NIH: HL075476 and ES09089.