Background: Endotoxin is a lipopolysaccharide (LPS) constituent of the outer membrane
of most gram negative bacteria. Ubiquitous in the environment, it has been implicated as a cause or
contributing factor in several disparate disorders from sepsis to heatstroke and Type II diabetes mellitus.
Starting at birth, the innate immune system develops cellular defense mechanisms against environmental
microbes that are in part modulated through a series of receptors known as toll-like receptors.
Endotoxin, often referred to as LPS, binds to toll-like receptor 4 (TLR4)/ myeloid differentiation
protein 2 (MD2) complexes on various tissues including cells of the innate immune system,
smooth muscle and endothelial cells of blood vessels including coronary arteries, and adipose tissue.
Entry of LPS into the systemic circulation ultimately leads to intracellular transcription of several
inflammatory mediators. The subsequent inflammation has been implicated in the development and
progression atherosclerosis and subsequent coronary artery disease and heart failure.
Objective: The potential roles of endotoxin and TLR4 are reviewed regarding their role in the pathogenesis
of atherosclerotic heart disease.
Conclusion: Atherosclerosis is initiated by inflammation in arterial endothelial and subendothelial
cells, and inflammatory processes are implicated in its progression to clinical heart disease. Endotoxin
and TLR4 play a central role in the inflammatory process, and represent potential targets for
therapeutic intervention. Therapy with HMG-CoA inhibitors may reduce the expression of TLR4 on
monocytes. Other therapeutic interventions targeting TLR4 expression or function may prove beneficial
in atherosclerotic disease prevention and treatment.