Aspirin Action in Endothelial Cells: Different Patterns of Response Between Chemokine CX3CL1/CX3CR1 and TNF-α/TNFR1 Signaling Pathways

TNF-alpha induces fractalkine (CX3CL1) and its receptor CX3CR1 in endothelial cells through NF-O > B activation. NF-O > B inhibitors may reduce the expression of CX3CL1, and modulation of the CX3CL1/CX3CR1 signaling was proposed as a new target for aspirin. We examined the effects of aspirin on CX3CL1 and TNF-alpha production, as well as CX3CR1 and TNFR1 expression. HUVECs isolated after term pregnancies (N = 28) were cultured in vitro. Lipopolysaccharide (1 mu g/ml) was used as CX3CL1 inducer. HUVECs were exposed to six different concentrations of aspirin (between 1.0 and 6.0 mM) during 7 days. The levels of CX3CL1 and TNF-alpha in the culture media were measured using ELISA. After termination of the cultures, mean expressions of CX3CR1 and TNFR1 were examined in the immunostained paraffin sections using quantitative immunohistochemistry. Aspirin significantly (p < 0.05) decreased CX3CL1 production, and the mean decrease in CX3CL1 production was inversely proportional to increased (p < 0.05) expression of CX3CR1. The combined mean CX3CL1 concentrations, including all time points, equaled 782.18 +/- 74.4 pg/ml in aspirin treated HUVECs compared to a total concentration of 2467.53 +/- 127.5 pg/ml combined from the respective time points in the controls. An inhibition of TNF-alpha production in HUVECs after pretreatment with aspirin was observed. Unlike in the case of CX3CR1 expression, there were no signs of TNFR1 upregulation. Autoregulation between CX3CL1 and CX3CR1 may explain overexpression of CX3CR1 as the compensatory effect in aspirin-treated HUVECs. Inhibition of CX3CR1 could prevent thrombotic complications in the early period after discontinuation of aspirin.