Abstract 1312: Smoking is Associated with Increased Platelet P2Y12 Expression, Mediated by Nicotine-Induced Upregulation.
Recent clinical trial data have demonstrated that smokers receive a more robust benefit from aspirin plus clopidogrel over aspirin alone relative to that acheived in non-smokers. Accordingly, we postulated that platelets from smokers might have enhanced expression of the clopidogrel target (P2Y12). We prepared platelet lysates from 10 healthy non-smokers and 10 active smokers (1.1 pack per day average consumption). Platelet lysates were subjected to immunoblotting for P2Y12, followed by stripping and reprobing for GAPDH. The P2Y12 : GAPDH ratio (Figure⇓) was significantly higher in smokers compared to nonsmokers (0.76 ± 0.13 vs. 1.24 ± 0.15, p<0.05). We then hypothesized that nicotine might be the active agent that induces P2Y12. Four cell lines (human coronary artery endothelial cells, umbilical vein endothelial cells, aortic smooth muscle cells, and megakaryoblastic cells) were cultured in the absence or presence of nicotine for 20 hours. Immunoblotting for P2Y12, P2Y2, and actin was performed. Nicotine, at 0.1 - 1.0 μM, induced P2Y12 (but not P2Y2) expression by 50% or more in all 4 cell lines. HASMC exhibited the greatest induction with a 6-fold mean increase in P2Y12 expression in response to 0.25 μM nicotine. The induction was inhibited by mecamylamine (MEC), a non-selective nicotinic acetylcholine receptor (nAChR) antagonist, suggesting that nAChR mediate the induction of P2Y12 expression by nicotine. In conclusion, platelets from smokers have higher expression of P2Y12, possibly accounting for enhanced relative benefit of clopidogrel in these patients. Nicotine upregulates P2Y12 in a variety of vascular cells, and is a likely mediator of this effect in platelets.