Date of download: 6/21/2016 Copyright © The American College of Cardiology. All rights reserved. From: The Multifaceted Clinical Readouts of Platelet Inhibition by Low-Dose Aspirin J Am Coll Cardiol. 2015;66(1): doi: /j.jacc Platelet Inhibition by Low-Dose Aspirin A wide repertoire of lipid and protein mediators, which may contribute to several clinical syndromes possibly responsive to low- dose aspirin therapy, are released upon platelet activation and aggregation. The figure illustrates inhibition of platelet prostanoid production by aspirin and its functional and clinical consequences. The lines of evidence supporting the protective effects of aspirin are summarized below each panel. AA = arachidonic acid; ASPREE = ASPirin in Reducing Events in the Elderly; RCT = randomized controlled trial(s); PGE2 = prostaglandin E2; PGH2 = prostaglandin H2; TXA2 = thromboxane A2. Figure Legend:

Date of download: 6/21/2016 Copyright © The American College of Cardiology. All rights reserved. From: The Multifaceted Clinical Readouts of Platelet Inhibition by Low-Dose Aspirin J Am Coll Cardiol. 2015;66(1): doi: /j.jacc Absolute Effects of Antiplatelet Therapy With Low-Dose Aspirin on the Risk of Vascular Events (Nonfatal MI, Nonfatal Stroke, or Death From Vascular Causes) in 5 Groups of High-Risk Patients The number needed to treat (NNT) ranged between 26 (acute myocardial infarction [MI]) to 100 (acute stroke) per month of treatment in the acute setting, and from 65 (previous MI) to 105 (previous stroke) per year of treatment in the secondary prevention setting. Figure Legend:

Date of download: 6/21/2016 Copyright © The American College of Cardiology. All rights reserved. From: The Multifaceted Clinical Readouts of Platelet Inhibition by Low-Dose Aspirin J Am Coll Cardiol. 2015;66(1): doi: /j.jacc Benefits and Risks of Low-Dose Aspirin in Primary Prevention Trials The numbers of vascular events avoided and episodes of major bleeding caused per 1,000 patients treated with aspirin per year are plotted from the results of individual placebo-controlled trials of aspirin in different patient populations characterized by various degrees of cardiovascular risk, as noted on the abscissa. Number needed to treat (NNT) and number needed to harm (NNH) values are given for subjects in 3 categories of risk on the basis of the presence or absence of randomized controlled trials. Modified with permission from Patrono et al. (5). ACCEPT-D = Aspirin and Simvastatin Combination for Cardiovascular Events Prevention Trials in Diabetes; ASCEND = A Study of Cardiovascular Events in Diabetes; ARRIVE = Aspirin to Reduce Risk of Initial Vascular Events; ASPREE = ASPirin in Reducing Events in the Elderly; BDT = British Doctors Trial; HOT = Hypertension Optimal Treatment Study; PHS = Physicians’ Health Study; PPP = Primary Prevention Project; SAPAT = Swedish Angina Pectoris Aspirin Trial; TPT = Thrombosis Prevention Trial; WHS = Women’s Health Study. Figure Legend:

Date of download: 6/21/2016 Copyright © The American College of Cardiology. All rights reserved. From: The Multifaceted Clinical Readouts of Platelet Inhibition by Low-Dose Aspirin J Am Coll Cardiol. 2015;66(1): doi: /j.jacc Platelet-Derived Mediators of the Inflammatory Response Activated platelets release inflammatory and mitogenic substances into the microenvironment, primarily altering the chemotactic, adhesive, and proteolytic properties of the endothelium. Pre-formed platelet mediators, stored in α-granules, can be released immediately after platelet activation through a process of exocytosis triggered by increased intracellular calcium levels. Activated platelets are also capable of time-dependent synthesis of protein mediators, such as tissue factor and interleukin-1β. CD40 ligand is stored in the cytoplasm of resting platelets and rapidly presents on the surface after platelet activation. After cleavage, to generate a soluble, functional fragment (soluble CD40 ligand), the mediator is released into the extracellular environment, inducing inflammatory responses in the endothelium by binding CD40 on endothelial cells. P-selectin is released from platelet granules and binds to the P-selectin glycoprotein ligand 1 (PSGL-1) receptor on monocytes, enhancing the adhesion of the monocytes to vascular-cell adhesion molecule (VCAM) 1 and the other adhesins expressed on activated endothelial cells and inducing the production of tissue factor by monocytes. Activated platelets also release chemokines that trigger the recruitment of monocytes (e.g., regulated on activation normal T-cell expressed and secreted [RANTES]) or promote the differentiation of monocytes into macrophages (e.g., platelet factor 4), as well as matrix-degrading enzymes such as matrix metalloproteinase (MMP) 2 or 9. Interleukin-1β is a major mediator of platelet-induced activation of endothelial cells, causing enhanced chemokine release and up- regulation of endothelial adhesion molecules to promote the adhesion of neutrophils and monocytes to the endothelium. H2O2 = hydrogen peroxide; ICAM = intracellular adhesion molecule; mRNA = messenger RNA; MCP = monocyte chemoattractant protein; O2– = superoxide anion; OH – = hydroxyl radical. Figure Legend: