Effect of C-reactive protein on Fcγ receptor II in cultured bovine endothelial cells

Abstract

The major CRP (C-reactive protein) receptor on leucocytes has been identified as the low-affinity IgG receptor Fcγ receptor II (CD32). Our aim was to assess whether inflammation may modify the presence of the CD32 receptor in BAEC (bovine aortic endothelial cells). Confocal microscopy experiments showed a weak expression of the CD32 receptor in control BAEC that was slightly increased by 10 μg/ml CRP. Incubation of BAEC with TNF-α (tumour necrosis factor-α) did not modify the fluorescence signal of CD32. Addition of CRP to TNF-α-incubated BAEC enhanced the fluorescence signal of the CD32 receptors. The CD32 receptors showed a perinuclear cytoplasmic localization in BAEC. An alteration of the NO (nitric oxide)-dependent vasorelaxation has been defined as endothelial dysfunction. Endothelial dysfunction has been associated with the presence of superoxide anion and with a reduction in the expression of the eNOS (endothelial NO synthase). A concentration of CRP similar to that detected in patients with cardiovascular risk (10 μg/ml) failed to modify the generation of superoxide anion stimulated by TNF-α. Western blot experiments showed that TNF-α decreased the expression of the eNOS protein, which was partially protected by treatment with 10 μg/ml CRP. The protective effect of 10 μg/ml CRP on eNOS expression in TNF-α-incubated BAEC was prevented by an antibody against CD32 receptors. In conclusion, the present results suggest that, although CRP has been associated with inflammation, CRP may protect the expression of eNOS protein against pro-inflammatory mediators such as TNF-α.