Increased production of hydrogen peroxide by peripheral blood monocytes associated with smoking exposure intensity in smokers

BACKGROUND: Smoking is known to be associated with oxidative stress; however, it has not been elucidated whether the oxidative response is influenced by the intensity of smoking exposure. OBJECTIVES: Evaluate the effect of smoking exposure on the secretion of hydrogen peroxide (H(2)O(2)) by the peripheral blood monocytes of smokers. METHODS: A total of 25 smokers (50.3±8.8 years, 48% male) underwent the following evaluations: spirometry, pulse oximetry, body composition and total peripheral blood count. Peripheral blood monocyte (PBM) cultures were isolated and maintained, and IL-6 and TNF-α were measured in the plasma and in the supernatants of spontaneous and stimulated cultures. H(2)O(2) was evaluated in the supernatants of the PBM cultures, and a subset of the PBM culture supernatants was stimulated with phorbol myristate acetate (PMA). We also evaluated 38 healthy controls (49.1±8.2 years, 42% male). RESULTS: The spontaneous and stimulated monocytes’ secretion of H(2)O(2) were statistically higher in the smokers than in the healthy controls (p<0.001). The H(2)O(2) secretions were statistically significant higher after stimulation with PMA in both groups (p<0.001). In the multiple regression analysis, we identified a positive, statistically significant association between pack-years of smoking and the spontaneous secretion of H(2)O(2) by PBM culture, adjusted for potential confounding variables. The association between PBM culture secretion of H(2)O(2) and the production of TNF-α and IL-6 was not significant. CONCLUSION: We identified a positive association between higher production of H(2)O(2) in smokers and higher smoking exposure during life. The influence of pack-years smoking may be a key modifiable factor in oxidative stress associated to smoking.