A 50-year-old man has a 2-year history of angina pectoris that occurs during exercise. On physical examination, his blood pressure is 135/75 mm Hg, and his heart rate is 79/min and slightly irregular. Coronary angiography shows a fixed 75% narrowing of the anterior descending branch of the left coronary artery. He has several risk factors for atherosclerosis: smoking, hypertension, and hypercholesterolemia. Which of the following is the earliest event resulting from the effects of these factors?

Atherosclerosis is thought to result from an initial endothelial injury and the subsequent chronic inflammation and repair of the arterial intima. All risk factors, including smoking, hyperlipidemia, and hypertension, cause biochemical or mechanical injury to the endothelium with resulting dysfunction that initiates smooth muscle migration with proliferation, as well as lymphocyte and monocyte-macrophage infiltration. Formation of foam cells occurs after the initial endothelial injury. Vasomotor tone does not play a major role in atherogenesis. Inhibition of LDL oxidation should diminish atheroma formation. Although lipoprotein receptor alterations can occur in some inherited conditions, these account for only a fraction of cases of atherosclerosis, and other lifestyle conditions do not affect their action.