Toll-like receptor 4 expressions on peripheral blood monocytes were enhanced in coronary artery disease even in patients with low C-reactive protein

Toll-like receptors (TLRs) play important roles in the pathogenesis of atherosclerosis. On the other hand, serum high sensitivity C-reactive protein (hsCRP) is known as an independent coronary risk factor, but cardiovascular events do occur even in low hsCRP levels. We investigated whether the TLR4 expression levels on human peripheral blood monocytes were associated with serum hsCRP levels or the occurrence of coronary artery diseases (CAD). One hundred CAD patients and 100 non-CAD subjects were enrolled. There were 72 non-CAD subjects and 53 CAD patients with low serum hsCRP levels. Among the low-hsCRP subjects, the TLR4 expression levels were higher in CAD patients than in non-CAD subjects (P < 0.05, after being adjusted for other risk factors). Moreover, TLR4 expression levels in stable angina pectoris (SAP) patients were elevated compared with those in non-CAD subjects (P < 0.05), and those in acute coronary syndrome patients were higher than SAP patients even in low-hsCRP subjects (P < 0.01). In conclusion, the TLR4 expression levels on peripheral blood monocytes in CAD patients were higher than those in non-CAD subjects and correlated with disease activity, even in low-hsCRP subjects. The combined measurement of serum hsCRP and the TLR4 expression on peripheral blood monocytes, especially among low-hsCRP subjects, may become a new coronary risk marker.