Abstract 3980: Effect of Smoking Cessation on the Number, Proliferation and Adhesive Properties of Endothelial Progenitor Cells
Endothelial progenitor cells (EPC) may participate in vascular repair, and studies reported that cardiovascular risk factors are associated with reduced circulating levels of EPC. In order to examine the effect of smoking cessation (SC) on EPC number and function, we prospectively followed (over 6 months) 124 smokers (50 men; mean age, 47.1±12.2 years) participating in a supervised 5-week SC program. In contrast to previous studies which focused on healthy young adults, additional cardiovascular risk factors or known cardiovascular disease were present in 59 (47.6%) and 9 (7.3%) of our patients, respectively. At the end of the 5-week intervention, participants had decreased smoking from 20.2 to 1.2 cigarettes per day, and 86% completely quit smoking. SC was associated with a significant decrease in plasma LDL cholesterol (P=0.001) and fibrinogen (P=0.0004) levels at 5 weeks, whereas a decrease in hsCRP levels was observed 6 months later (2.2±1.8 vs. 1.4±1.1 mg/L; P=0.025). SC did not significantly alter the number of circulating CD34+, VEGF-R2+ cells (0.19±0.18 vs. 0.17±0.18%; P=0.88), or the number of EPC colony forming units (43±46 vs. 58±46 EPC-CFU; P=0.22). On the other hand, fewer acLDL+, lectin+ cells could be expanded ex vivo after SC (197±166 vs. 124±105 cells; P=0.0001), and this effect persisted 6 months later (112±83 cells). Interestingly, the decrease in acLDL+; lectin+ cells after SC was particularly pronounced in persons with additional cardiovascular risk factors. Further studies revealed that SC was associated with reduced adhesion of acLDL+ cells to fibronectin-coated culture dishes (60±26 vs. 35±16 cells; P=0.001), and to mature endothelial cells (30±14.1 vs. 21±12; P=0.003). As the reduction of EPC adhesion after SC might be related to a reduction in oxidative stress, we determined plasma levels of asymmetric dimethyl arginine (ADMA), a competitive inhibitor of endothelial nitric oxide synthase. ADMA levels significantly decreased after SC (from 0.70±0.13 to 0.66±0.15 μmol/L; P=0.008). The results of this ongoing study were partly unexpected in view of previous reports. They suggest that smoking and smoking cessation may modulate EPC function, particularly adhesion, rather than circulating EPC numbers.