C-reactive protein in atherosclerosis: A causal factor?

Atherosclerosis is considered a to be multifactorial disease driven by inflammatory reactions. The process of inflammation also contributes to the pathogenesis of acute atherothrombotic events. C-reactive protein (CRP) is an acute phase protein and its concentration in serum reflects the inflammatory condition of the patient. Levels of CRP are consistently associated with cardiovascular disease (CVD) and predict myocardial infarctions and stroke. Since CRP is present in the atherosclerotic lesion, it may actively contribute to the progression and/or instability of the atherosclerotic plaque. The role of CRP in inflammation and its causality in atherosclerosis are the subject of many investigations but are not yet fully elucidated. This review focuses on recently identified mechanisms by which CRP may modulate and evolve the process of atherosclerosis. We discuss the function of CRP and review the most recent evidence for an independent role of CRP in the development of atherosclerosis. Many studies suggest such a role, but a number of the described effects may be the result of contamination of the CRP preparations.

C-reactive protein does not directly induce tissue factor in human monocytes.

OBJECTIVE: It is generally assumed that C-reactive protein (CRP) induces synthesis of tissue factor (TF) in monocytic cells, thereby potentially initiating intravascular blood coagulation. We aimed to elucidate the mechanism of CRP-induced TF expression in monocytes and monocyte-derived macrophages (MDMs) in vitro. METHODS AND RESULTS: Monocytes were isolated from the blood of healthy donors and cultured with or without CRP or lipopolysaccharide (LPS) to study the time course of TF antigen and TF mRNA expression. Addition of 100 microg/mL CRP did not result in a significant increase in TF antigen (range: 9 to 163 pg/10(6) cells, n=11) and TF mRNA (relative number of TF transcripts; N(TF)=0.01 to 0.33), when compared with nonstimulated cells (TF antigen 7 to 46 pg/10(6) cells, N(TF)=0.01 to 0.13). Variation of CRP concentration and exposure time did not affect the TF response. Similar results were obtained in monocytes cultured in suspension and in MDMs. In contrast, TF was strongly induced by 10 microg/mL LPS (TF antigen 1125 to 6120 pg/10(6) cells, N(TF)=5.94 to 23.43). Cultured monocytes did express FcRgammaII, a putative CRP receptor, and addition of CRP induced a 7-fold increase in the production of monocyte chemoattractant protein-1 (MCP-1). Interestingly, CRP addition to peripheral blood mononuclear cells (PBMCs) did result in TF expression on monocytic cells. CONCLUSIONS: The absence of TF induction after incubation of purified monocytes with CRP indicates that CRP is unable to induce TF expression in monocytes and MDMs directly. The presence of CRP-induced TF expression in PBMCs suggests that CRP can induce TF indirectly, probably through cross-talk between cells.