Modulation of fractalkine receptor (CX3CR1) expression on human monocytes

M. V. RAMOS; G. C. FERNANDEZ; V. I. LANDONI; R. J. FERNÁNDEZ BRANDO; L. V. BENTANCOR; M. A. ISTURIZ; M. S. PALERMO

Rio de Janeiro, Brasil

Congreso; 13th International Congress of Immunology; 2007

Fractalkine (FKN) is an anchored-membrane chemokine present on inflamed endothelium. FKN may contribute to Hemolytic Uremic Syndrome (HUS) pathogenesis capturing cytotoxic cells that express FKN-receptor (CX3CR1) from blood like monocytes (Mo) and NK cells. Since we found CX3CR1+-Mo decreased in HUS patients, we analyzed modulation of CX3CR1- expression in Mo by soluble factors present in HUS. Human Mo were purified and incubated 4 or 20 h in presence of medium, LPS,  IL-10 or IFN-ã. Then, CX3CR1 expression was studied by flow cytometry. After 20 h Mo showed a reduced % of CX3CR1+ cells. This effect was accelerated by LPS (100 ng/ml), but abolished by IL-10 (10ng/ml) or IFN-ã (240U/ml): Medium: 0h=80±2%; 4h=79±2%; 20h= 49±4%*; 4h LPS= 62±3%*; 20h IL-10=73±4%#; 20h IFN-ã=67±9# (*p<0.05 vs 0h, #p<0.05 vs 20h medium; n=8). A similar effect was observed in THP-1 cells, a CX3CR1+-monocytic cell line. These cells were differentiated with PMA (5ng/ml) for 48h, and incubated with IL-10 or IFN-ã, for 20h. There was an increase in CX3CR1 expression (% and median of fluorescence intensity, MFI) in presence of IL-10 or IFN-ã: medium:67±3%,MFI:30±3; IL-10: 81±3%*,MFI:43±6*, IFN-ã:72±6%*,MFI:98±15* (*p<0.05 vs medium, n=7). Two inhibitors of PI3K (LY294002, 30ìM and wortmanin (Wo), 100nM), inhibited IL-10 effects on both Mo and THP-1 cells. (Mo: 20h IL-10+Wo=29±9%; IL-10+Ly=49±8%, n=3, p<0.05 vs IL-10; THP-1: IL-10+Wo=55±8%; IL-10+Ly=56±7%, n=3, p<0.05 vs IL-10). Similar effects were seen with IFN-ã. We conclude that CX3CR1 expression can be modulated by inflammatory/anti-inflammatory factors, and that Akt phosphorylation could be involved in both, IFN-ã and IL-10 signalling pathways.