Serum amyloid A activation of human coronary artery endothelial cells exhibits a neutrophil promoting molecular profile

•Inducible TLR2 is highly expressed in human coronary artery endothelial cells (HCAEC).•SAA stimulates TLR2 expression in a time-dependent manner.•SAA significantly induces released protein levels of GM-CSF, MCP-1 and sVCAM-1 through TLR2.•SAA positive feedback signaling in HCAEC is TLR2-, but not ERK1/2- dependent.•SAA induces a predominantly neutrophil-activating profile of cytokines, chemokines and adhesion molecules in HCAEC.

BackgroundSerum amyloid A (SAA) has been shown to be an active participant in atherosclerosis and cardiovascular diseases. SAA-stimulated human coronary artery endothelial cells (HCAEC) were reported to release pro-inflammatory cytokines, chemokines and adhesion molecules; however it remains unclear which putative SAA receptors are present in these cells and how they act. We investigated the effects of inflammatory stimuli on the expression of SAA receptors, signaling pathways and molecular profiles in HCAEC.Methodology/principle findingsHCAEC were cultured in vitro and stimulated with SAA (1000 nM) or IL-1β (1000 pg/ml). Expression of mRNA was determined by qPCR, and expression and quantification of proteins were assessed by dot array blots and ELISA, respectively. Protein phosphorylation was determined by dot blot arrays and Western blots. We report that all potential SAA receptors tested (FPR2/ALX, RAGE, TANIS, TLR2, TLR4 and CLA-1/hSR-B1) are expressed in HCAEC. Importantly, IL-1β or SAA significantly increased solely the expression of the innate immune receptor TLR2. SAA upregulated the phosphorylation of ERK1/2, NF-κB (p65, p105) and JNK, as well as expression/release of IL-6, IL-8, G-CSF, GM-CSF, ICAM-1 and VCAM-1, all potent molecules involved in neutrophil-related activities. A TLR2-dependent positive feedback mechanism of SAA expression was found.Conclusion/significanceSAA stimulated responses in HCAEC target neutrophil rather than monocyte/macrophage activation.