Endotoxin, TLR4 signaling and vascular inflammation: potential therapeutic targets in cardiovascular disease

Cardiovascular disease ranks among the leading causes of morbidity and mortality in adult populations in the Western world. Significant progress in understanding the etiology of cardiovascular disease has come from recent recognition that chronic inflammation plays a key role in its development. The principal mediators of this inflammatory response, and the mechanisms by which they work, however, are incompletely understood. Moreover, the complex nature of the inflammatory response poses significant challenges to the development of effective and targeted treatments. Potentially promising targets to reduce inflammation in atherosclerosis include Toll-like receptor (TLR) pathways and anti-inflammatory factors that modulate TLR signaling. In this review, we outline studies that provide insight into the links between cardiovascular disease and inflammation, focusing on innate immunity and endotoxin/TLR4 signaling. We also discuss the contribution of specific host immune/inflammatory responses to atherogenesis, and describe cellular signaling pathways (lipopolysaccharide-binding protein [LBP], CD14, MD-2, TLR4, MyD88, and NF-kappaB, among others) that play key roles in innate immune signaling. Finally, we discuss the therapeutic potential of modulating these cellular signaling pathways as future strategies for the prevention and treatment of cardiovascular disease, including such approaches as specific targeting of the TLR4 signaling pathway, antibiotic therapy, drug classes with broad anti-inflammatory activity (statins, thiazolidinediones), and the potential of vaccine development. Because of the complexity of the links between low-level chronic infections, inflammation, and atherosclerosis, treatment and prevention of cardiovascular disease will likely require an integrated approach that utilizes a combination of these strategies to target the underlying inflammatory processes.