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Updated: Aug 18, 2026
Quantification of Monocyte Chemotactic Activity In Vivo and Characterization of Blood Monocyte Derived Macrophages
Published on: August 12, 2019
Macrophage conditioned medium induces the expression of C-reactive protein in human aortic endothelial cells:
Senthil Kumar Venugopal1, Sridevi Devaraj, Ishwarlal Jialal
1Laboratory for Atherosclerosis and Metabolic Research, Department of Pathology and Laboratory Medicine, University of California Medical Center, Sacramento, CA 95817, USA.
Insights
C-reactive protein (CRP) is produced by human aortic endothelial cells, particularly when stimulated by interleukin-1 and -6. Macrophage-conditioned media significantly increases CRP production, suggesting a role in atherosclerosis.
Area of Science:
- Cardiovascular Research
- Immunology
- Cell Biology
Background:
- C-reactive protein (CRP) is a known risk marker for cardiovascular events.
- CRP is produced not only in the liver but also in atherosclerotic lesions, kidney, neurons, and alveolar macrophages.
- Proatherogenic effects of CRP in endothelial cells are documented.
Purpose of the Study:
- To investigate C-reactive protein (CRP) production in human aortic endothelial cells (HAEC).
- To identify the specific cytokines that stimulate CRP production in HAEC.
- To explore the influence of vascular smooth muscle cells (VSMC) and macrophages on HAEC CRP production.
Main Methods:
- Detection of CRP mRNA via RT-PCR and in situ hybridization.
- Analysis of intracellular and secreted CRP protein using Western blot and ELISA.
- Incubation of HAEC with cytokines (IL-1, IL-6, TNF) and conditioned media from VSMC and macrophages (MCM).
Main Results:
- CRP mRNA, intracellular protein, and secreted protein were detected in HAEC.
- The combination of interleukin-1 (IL-1) and interleukin-6 (IL-6) was the most potent agonist for CRP production in HAEC.
- Macrophage-conditioned media (MCM) significantly increased CRP synthesis and secretion by HAEC, an effect reversible by inhibiting IL-1 and IL-6.
Conclusions:
- Human aortic endothelial cells (HAEC) synthesize and secrete C-reactive protein (CRP).
- Cytokines IL-1 and IL-6, particularly in combination, strongly stimulate CRP production in HAEC.
- Local production of CRP within atherosclerotic lesions, potentially driven by macrophage-derived factors, may lead to elevated concentrations contributing to inflammation and atherogenesis.
Abstract:
C-reactive protein (CRP) is a risk marker for cardiovascular events in apparently healthy persons. Cogent data show that, aside from the liver, CRP is produced in atherosclerotic lesions, kidney, neurons, and alveolar macrophages. Because several proatherogenic effects of CRP have been documented in endothelial cells, we examined human aortic endothelial cells (HAEC) for CRP production. We detected the presence of CRP mRNA by RT-PCR and in situ hybridization, intracellular protein by Western blot and secreted protein by ELISA. Coincubation with the cytokines interleukin (IL)-1, IL-6, and tumor necrosis factor alone and in combination showed that the most potent agonist for CRP production from HAEC is the combination of IL-1 and IL-6 (P < 0.05). To mimic the in vivo situation, we examined whether vascular smooth muscle cell (VSMC) and/or macrophage conditioned media (MCM) could augment CRP production by HAEC. While VSMC-conditioned media had no effect, incubation with MCM resulted in a significant twofold increase in the synthesis of both intracellular and secreted CRP (P < 0.05). The effect of MCM could be reversed by inhibiting both IL-1 and IL-6. Thus, stimulated synthesis and secretion of CRP by cells in the atherosclerotic lesion by paracrine/autocrine loops could result in local concentrations of CRP far in excess of plasma concentrations and could contribute to proinflammatory, proatherogenic effects.
