Tobacco smoking increases leukocyte activation and decrease regulatory T cells in healthy subjects

Abstract

Tobacco use is a major risk factor for heart attacks, strokes, chronic obstructive pulmonary disease (COPD), emphysema, and cancer. Smoking promotes inflammation and thrombosis through a poorly understood mechanism. Whether if the immune response is significantly affected by smoking is not well established. We studied different leukocytes subpopulations and its activation by flow cytometry, in a very well characterized population of healthy subjects. With previous authorization by the Ethics Committees of the institution and signed informed consent, we enrolled 55 healthy subjects, 16 current smokers (S) and 39 non smokers (NSm). The median age was 49 years (27-76). Sm had history of tobacco smoking of at least 10 cigarettes/day, and had smoked normally the day before. Each participant was screened for diabetes, dyslipidemia, hypertension and subclinical atheromatosis disease: intima-media thickness of the common carotid arteries (CCA), presence of internal or external carotid arteries plaque, arterial stiffness (carotid-femoral pulse wave velocity), endothelial function by reactive hyperemia and aortic central pressure estimation (radial pressure wave analysis). Subjects with any comorbidity as autoimmune disease, infection, cardiovascular disease, clinical chronic obstructive pulmonary disease were excluded. Sm showed a decrease on neutrophils percentage (p=0.01) and a marked increase in the expression of CD69 (activation antigen) in neutrophils (p=0.044) and monocytes (p=0.011). CD56 bright CD16-NK subset (immunomodulatory NK subset) was decreased on Sm group (p=0.002) despite no difference was observed in total NK cells between groups. Additionally, Sm also showed approximately a marked decrease in the percentage of regulatory T cells (CD4+CD25+highFoxP3+) on peripheral blood (p=0.002). No differences were found neither neither in CD4, CD8 T lymphocytes and B lymphocytes nor in lymphocytes activation markers and intracellular cytokines (IFN-γ IL-4, IL-10, IL-17) between groups. The presence/absence of subclinical atherosclerotic disease, diabetes, dyslipi-demia, hypertension or Framingham risk score did not significantly alter these results. These results indicate that tobacco smoking affects innate and adaptive immune responses. Our data shows a regulatory T cells reduction and an increase on leukocytes status activation in cigarette smoking. Our data suggests a potential link between smoking and inflammation - thrombosis.