Effects of C-Reactive Protein on CC Chemokine Receptor 2-Mediated Chemotaxis of Monocytes

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Periodontal infections can increase patients' serum C-reactive protein (CRP) level, which is a predictive marker of future cardiovascular events. Serum CRP may be a key mediator associating periodontitis with cardiovascular disease. It is not yet clarified whether the chemotactic activity of monocytes changes with increased serum CRP. This study investigated the influence of CRP on monocyte chemotaxis and the effects of CRP on CC chemokine receptor 2 (CCR2) expression by monocytes in vitro. Monocyte cell line THP-1 was cultured with human recombinant CRP of different final concentrations, which were 2, 4, 6, 8, and 10 mg/L, respectively. After 24 h incubation, Transwell chambers were applied to analyze the chemotactic activity of pretreated monocytes. Flow cytometry analysis and real-time reverse transcription-polymerase chain reaction (RT-PCR) were applied to detect the CCR2 protein and gene expression levels. In Transwell chambers, more cells were attracted in CRP-pretreated groups than that of blank control with no CRP (p<0.05). The chemotaxis activity was stronger in higher CRP concentration groups than lower ones (p<0.05). The CCR2 protein and mRNA expression was increased in a CRP concentration-dependent manner (p<0.05). CRP stimulation may induce CCR2 overexpression on monocytes and then promote the chemotaxis ability of monocytes. This result suggests that increased serum CRP concentration of periodontitis patients may be associated with high risk of cardiovascular disease.