C-Reactive Protein Upregulates Angiotensin Type 1 Receptors in Vascular Smooth Muscle

Abstract

Background— Accumulating evidence suggests that C-reactive protein (CRP), in addition to predicting vascular disease, may actively facilitate lesion formation by inciting endothelial cell activation. Given the central importance of angiotensin type 1 receptor (AT 1 -R) in the pathogenesis of atherosclerosis, we examined the effects of CRP on AT 1 -R expression and kinetics in vascular smooth muscle (VSM) cells. In addition, the effects of CRP on VSM migration, proliferation, and reactive oxygen species (ROS) production were evaluated in the presence and absence of the angiotensin receptor blocker, losartan. Lastly, the effects of CRP (and losartan) on neointimal formation were examined in vivo in a rat carotid angioplasty model. Methods and Results— The effects of human recombinant CRP (0 to 100 μg/mL) on AT 1 -R transcript, mRNA stability, and protein expression were studied in cultured human VSM cells. AT 1 -R binding was assessed with 125 I-labeled angiotensin II (Ang II). VSM migration was assessed with wound cell migration assays, whereas VSM proliferation was determined with [ 3 H]-incorporation and cell number. The effects of CRP (and losartan) on Ang II–induced ROS production were evaluated by 2′,7′-dichlorofluorescein fluorescence. Lastly, the effects of CRP (and losartan) on neointimal formation, VSM cell migration, proliferation, and matrix formation were studied in vivo in a rat carotid artery balloon injury model. CRP markedly upregulated AT 1 -R mRNA and protein expression and increased AT 1 -R number on VSM cells. CRP promoted VSM migration and proliferation in vitro and increased ROS production. Furthermore, CRP potentiated the effects of Ang II on these processes. In the rat carotid artery angioplasty model, exposure to CRP resulted in an increase in cell migration and proliferation, collagen and elastin content, and AT 1 -R expression, as well as an increase in neointimal formation; these effects were attenuated by losartan. Conclusions— CRP, at concentrations known to predict cardiovascular events, upregulates AT 1 -R–mediated atherosclerotic events in vascular smooth muscle in vitro and in vivo. These data lend credence to the notion that CRP functions as a proatherosclerotic factor as well as a powerful risk marker.