Inflammatory Cytokines Stimulated C-Reactive Protein Production by Human Coronary Artery Smooth Muscle Cells

Abstract

Background - Serum C-reactive protein (CRP) levels are good predictors of the development of cardiovascular events in apparently healthy men and women. CRP has been believed to be produced exclusively by hepatocytes during the acute-phase response. Several lines of evidence have suggested that atherosclerotic arteries can also produce CRP. However, the cell types that produce CRP locally in the atherosclerotic arterial wall have not been clearly identified. Methods and Results - Human coronary artery smooth muscle cells (HCASMCs) and human umbilical vein endothelial cells (HUVECs) were incubated with interleukin-1β (IL-1β), IL-6, their combination, tumor necrosis factor-β (TNF-β), or lipopolysaccharide (LPS) at different concentrations. The supernatants were concentrated and analyzed by a high-sensitivity enzyme-linked immunosorbent assay specific for human CRP. RNA was extracted from the HCASMCs for reverse transcriptase-polymerase chain reaction (RT-PCR) using specific primers for the CRP. Maximal CRP production was observed in HCASMCs after 48 hours of incubation with the combination of 25 ng/mL of IL-1β and 10 ng/mL of IL-6, whereas incubation with IL-1β or IL-6 alone only modestly induced CRP. Incubation with TNF-α (50 ng/mL) or LPS (1000 EU/mL) resulted in an increase in CRP production comparable to the IL-1β and IL-6 combination. The induction of CRP in HCASMCs was independently confirmed by RT-PCR comparing the relative CRP mRNA levels. The induction of CRP production by HCASMCs was not reproduced in HUVECs, however. Conclusions - These results demonstrated that HCASMCs, but not HUVECs, could produce CRP in response to inflammatory cytokines. The locally produced CRP could directly participate in atherogenesis and the development of cardiovascular complications.