Background: C-reactive protein (CRP) may have proatherogenic but also vasoprotective properties. We tested the hypothesis that the configuration of CRP (pentameric, or native [nCRP], versus monomeric, or modified [mCRP]) determines these different characteristics in an in vivo model.
Methods and results: We investigated the effects of human nCRP and mCRP on the development of atherosclerosis in apolipoprotein E-knockout (ApoE(-/-)) mice. Treatment with nCRP for 8 weeks (2.5 mg/kg SC weekly) resulted in a 4-fold-higher mean aortic plaque area in 14-week-old female ApoE(-/-) mice compared with the saline controls. In contrast, mean plaque size was decreased by approximately 50% in mCRP-treated ApoE(-/-) mice (2.5 mg/kg SC weekly). Using immunohistochemistry, we report the natural presence of the mCRP antigen in saline controls. mCRP antigen was expressed in smooth muscle cells and extracellularly in the vicinity of the plaques to a similar level in both CRP-treated groups and saline controls. mCRP and ApoB colocalized with macrophages and were equally upregulated in all aortic plaques. Vascular cell adhesion molecule expression was increased, and CD154 and intercellular adhesion molecule showed a trend for higher expression in nCRP-treated compared with mCRP-treated mice. CD154 expression in the vessel wall and plaque size correlated significantly. mCRP-treated ApoE(-/-) exhibited higher serum levels of the antiinflammatory interleukin-10 compared with the other 2 groups.
Conclusions: Here, we show that mCRP and nCRP have opposite effects on atherosclerosis in ApoE(-/-) mice. These data may explain in part the conflicting activities previously reported for CRP in models of atherogenesis.