Toll-like receptors and atherosclerosis: key contributors in disease and health?

The identification of Toll-like receptors (TLRs) as key patternrecognition receptors of innate immunity has opened inquiries into previously unknown disease mechanisms. The ability of TLRs to detect a spectrum of pathogen-derived molecules defines their importance in innate immunity and provides a mechanistic link between infection and disease. Atherosclerosis is a chronic inflammatory disease where immune and metabolic factors interact to initiate and propagate arterial lesions. An understanding of TLRs in atherosclerosis could clarify the etiology of this complex process. Furthermore, the existence of host-derived endogenous TLR ligands may implicate TLR involvement in disease mechanisms beyond innate immunity, such as a role in homeostatic mechanisms to resolve injury. Our current knowledge of TLRs in atherosclerosis is discussed in this review with emphasis on experimental studies in atherosclerosis-susceptible mouse models. Highlights from studies of TLR involvement in other disease processes have demonstrated that TLR-dependent mechanisms probably parallel those found in atherosclerosis, some of which could be important in mitigating atherosclerotic injury. Finally, an appreciation of the pro- and anti-atherosclerotic mechanisms of TLR activation over the entire lifetime of an organism will provide clues to the role of TLRs in both health and disease.