Review
Current Understanding of Atherogenesis

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Abstract

Scientific understanding of atherogenesis is constantly developing. From Virchow's observations 160 years ago we now recognize the endothelial response to injury as inflammatory, involved in all stages of atherosclerosis. Endothelial activation may cause reversible injury or dysfunction, or lead to irreparable damage. Indeed, early atherosclerosis is reversible. The introduction of genome-wide association testing has furthered the identification of potentially important genetic variants that help explain the heritability of coronary artery disease as well as spontaneous cases of severe coronary artery disease in patients with otherwise minimal risk factors. However, the mechanisms by which many of the newer variants exert their influence remain unknown.

Section snippets

Normal Arterial Structure

Healthy human arteries have a tri-laminar structure (Figure 1).1 The tunica intima is an inner layer of endothelial cells lining the lumen called the endothelium. The endothelium is in direct contact with blood flow, and arterial endothelial cells possess many highly regulated mechanisms that are of vital importance in maintaining vascular homeostasis. Although often described as a monolayer, in human adults it is usually a more complex and heterogeneous structure containing some smooth muscle

Normal Endothelial Function

The normal, healthy endothelium is the major regulator of vascular homeostasis—maintaining the balance between vasodilation and vasoconstriction, inhibition and stimulation of smooth muscle cell proliferation and migration, and thrombogenesis and fibrinolysis (Table 1).3 Initial insight as to the importance of the endothelium in vasomotor modulation came from animal experiments during the 1980s.4, 5, 6, 7, 8, 9 It subsequently became evident that the endothelium is an active paracrine,

Endothelial Activation, Injury, and Dysfunction

Endothelial disturbance is characterized by distinct, often overlapping, phases.11 Endothelial activation occurs in 2 stages and represents a change from the quiescent phenotype described above toward one that involves the host defense response (characterized by the expression of proinflammatory substances, eg, cytokines), which may be physiologic, for example in response to infection,17 or pathophysiologic, in the presence of cardiovascular risk factors. Essentially, a reduction of nitric

The Impact of Conventional Modifiable and Nonmodifiable Cardiac Risk Factors on Endothelial Function in Patients with and without Coronary Artery Disease

Numerous studies have examined the effect of conventional modifiable and nonmodifiable risk factors on endothelial function because endothelial activation and dysfunction occur early in the evolution of coronary artery disease. Tables 220, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55 and 332, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70 represent a summary of key data. According to

Nonconventional Cardiac Risk Factors

A number of serologic markers of arterial vulnerability are currently recognized.77 Most are a reflection of endothelial injury (ie, risk markers) but have not been found to have a causal relationship with coronary artery disease. Possibly with the exception of high sensitivity C-reactive protein78 and homocysteine,79 most current cardiovascular biomarkers add little primary predictive value to traditional risk factors.80

A Brief History

The first reports of “hardening of the arteries” were recorded as early as the 16th century.81 In the mid- to late 18th century William Heberden was among the first of a group of English physicians to describe “a disorder of the breast” (anginal chest pain).82 He and colleagues Edward Jenner and Caleb Hillier Parry also described the process of calcification of the coronary arteries.83 In 1911 Sir Marc Ruffer was able to identify degenerative arterial changes suggestive of atherosclerosis in

Summary

Under normal homeostatic conditions the endothelium maintains vascular tone and blood fluidity with minimal expression of proinflammatory factors. Coronary artery disease is a chronic, multistage, inflammatory disease beginning in the second and third decade of life. Progression depends on the balance of endothelial activation, injury, and repair. The principal acute complication (and main cause of mortality) is myocardial infarction, usually occurring as a consequence of plaque rupture or

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    Funding: RAB was supported by a Rosetrees Medical Research Trust grant number M430.

    Conflict of Interest: None.

    Authorship: All authors had access to data used for manuscript preparation and a role in writing the manuscript.

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