Influence of an intravenous fish oil emulsion on monocyte-endothelial interactions

Introduction

Monocyte adhesion contributes to perfusion abnormalities, tissue damage and activation of the coagulation system during overwhelming inflammation. This study was performed to determine whether an intravenous fish oil emulsion for parenteral nutrition may attenuate monocyte–endothelial interactions under flow and reduce procoagulant activity, measured as tissue factor (TF) expression on adherent monocytes.

Methods

Human vascular endothelial cells were incubated with either a 10% intravenous fish oil emulsion (Omegaven^™, Fresenius Kabi) or a conventional ω-6 lipid emulsion (Intralipid^™, Pharmacia Upjohn) at 0.05–1 mg/ml for 24 h. Six hours following activation with TNFα (25 ng/ml), expression of endothelial cell adhesion molecules was measured by flow cytometry. Adhesion of isolated monocytes to pretreated endothelium was examined in a parallel plate flow chamber at postcapillary shear forces of 1.5 dyn/cm². Following perfusion, the cells were cocultured for additional 4 h and TF-expression on monocytes was determined by flow cytometry.

Results

In contrast to ω-6 lipids, fish oil downregulated CD62E, ICAM-1 and VCAM-1 in a dose-dependent manner. CD62P, however, remained unchanged. The changes in adhesion molecule expression were accompanied by a significant reduction of firm adhesion to 54%, whereas rolling interactions remained unchanged. In contrast to monocyte adhesion, fish oil had no effect on TF expression of cocultured monocytes.

Conclusion

Intravenous fish oil emulsions reduce both, endothelial cell adhesion molecule expression and monocyte adhesion. However, under flow conditions, rolling interactions via P-selectin remain unaltered. The functional importance of this effect is illustrated by the corresponding upregulation of TF in response to residual monocyte-endothelial interactions.