C-reactive Protein Upregulates Receptor for Advanced Glycation End Products Expression and Alters Antioxidant Defenses in Rat Endothelial Progenitor Cells

Object: The receptor for advanced glycation end products (RAGE) may play an important role in inflammatory processes and endothelial activation, likely to accelerate the processes of atherosclerosis, especially in patients with diabetes. The factors that regulate the expression of RAGE are not completely clear. C-reactive protein (CRP) is identified as a key proinflammatory cytokine in patients with atherosclerosis. Atherosclerosis also induces reduction and dysfunction of endothelial progenitor cells (EPCs), a main cell type for vascular repair. Therefore, we tested the hypothesis that CRP can regulate RAGE expression and alter antioxidant defenses in EPCs.

Methods And Results: EPCs, isolated from bone marrow, were cultured in the absence or presence of lipopolysaccharide-free CRP (5, 10, 15, 20, and 50 microg/mL). RAGE protein expression was measured by flow cytometric analysis and Western blot. RAGE messenger RNA expression was detected by polymerase chain reaction. Reactive oxygen species (ROS) were analyzed using the ROS assay kit. A spectrophotometer was used to assess superoxide dismutase and glutathione peroxidase activity, and polymerase chain reaction was used to test messenger RNA expression of superoxide dismutase and glutathione peroxidase. Apoptosis was evaluated by Annexin V immunostaining. Coculturing with CRP caused a significant upregulate expression of RAGE in EPCs, increased ROS production, altered antioxidant defenses, and induced EPC apoptosis. In addition, these effects were attenuated during blocking RAGE protein expression by small interfering RNA.

Conclusions: CRP at concentrations known to predict cardiovascular event may serve to impair EPC antioxidant defenses for upregulating the expression of RAGE and promote EPC sensitivity toward oxidative stress-mediated apoptosis. These data further support a direct role of CRP in the development and/or progression of atherosclerosis.