Mechanisms of disease: Toll-like receptors in cardiovascular disease

The innate immune system detects highly conserved, relatively invariant structural motifs of pathogens. Toll-like receptors (TLRs) have been identified as the primary innate immune receptors. TLRs distinguish between different patterns of pathogens and activate a rapid innate immune response; however, TLRs can also be activated by host-derived molecules. In addition to being expressed in immune cells, TLRs are expressed in other tissues, such as those of the cardiovascular system. TLRs could, therefore, be a key link between cardiovascular disease development and the immune system. Indeed, evidence that TLR activation contributes to the development and progression of atherosclerosis, cardiac dysfunction in sepsis, and congestive heart failure, is convincing. Although much has been learned about TLR activation in cellular components of the cardiovascular system, the role individual TLR family members have in the pathophysiology of cardiovascular diseases and hence in clinical practice remains to be defined. Here we review the rapid progress that has been made in this field, which has improved our understanding of vascular as well as myocardial TLR function in basic and clinical science.