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 (H2O2) 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-alpha were measured in the plasma and in the supernatants of spontaneous and stimulated cultures. H2O2 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 H2O2 were statistically higher in the smokers than in the healthy controls (p<0.001). The H2O2 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 H2O2 by PBM culture, adjusted for potential confounding variables. The association between PBM culture secretion of H2O2 and the production of TNF-alpha and IL-6 was not significant.Conclusion: We identified a positive association between higher production of H2O2 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.