Toll-like Receptor 4 Polymorphisms and Atherogenesis

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Abstract
The ability to mount a prominent inflammatory response to bacterial pathogens confers an advantage in innate immune defense but may signal an increased risk of atherosclerosis. We determined whether recently discovered genetic variants of toll-like receptor 4 (TLR4) that confer differences in the inflammatory response elicited by bacterial lipopolysaccharide are related to the development of atherosclerosis. As part of the five-year follow-up in the Bruneck (Italy) Study, we screened 810 persons in the study cohort for the TLR4 polymorphisms Asp299Gly and Thr399Ile. The extent and progression of carotid atherosclerosis were assessed by high-resolution duplex ultrasonography. As compared with subjects with wild-type TLR4, the 55 subjects with the Asp299Gly TLR4 allele had lower levels of certain proinflammatory cytokines, acute-phase reactants, and soluble adhesion molecules, such as interleukin-6 and fibrinogen. Although these subjects were found to be more susceptible to severe bacterial infections, they had a lower risk of carotid atherosclerosis (odds ratio, 0.54; 95 percent confidence interval, 0.32 to 0.98; P=0.05) and a smaller intima–media thickness in the common carotid artery (regression coefficient, –0.07; 95 percent confidence interval, –0.12 to –0.02; P=0.01). The Asp299Gly TLR4 polymorphism, which attenuates receptor signaling and diminishes the inflammatory response to gram-negative pathogens, is associated with a decreased risk of atherosclerosis. This finding is consistent with the hypothesis that innate immunity may play a part in atherogenesis.
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