Medium-chain, triglyceride-containing lipid emulsions increase human neutrophil beta(2) integrin expression, adhesion, and degranulation

Background: To test the hypothesis that lipid emulsions with different trig lyceride structures have distinct immunomodulatory properties, we analyzed human neutrophil adhesion and degranulation after lipid incubation. Methods : Neutrophils, isolated from the blood of 10 healthy volunteers, were incub ated in medium or physiologic (2.5 mmol/L) emulsions containing long-chain (LCT), medium-chain (MCT), mixed LCT/MCT, or structured (SL) triglycerides. Expression of adhesion molecules and degranulation markers was evaluated b y flow cytometry. Also, functional adhesion was investigated by means of a flow cytometric assay using fluorescent beads coated with the integrin liga nd intercellular adhesion molecule (ICAM)-1. Results: Although LCT and SL h ad no effect, LCT/MCT significantly increased expression of the beta(2) int egrins lymphocyte-function-associated antigen 1 (+18%), macrophage antigen 1 (+387%), p150,95 (+82%), and alpha(D)beta(2) (+230%). Degranulation marke r expression for azurophilic (CD63, +210%) and specific granules (CD66b, +3 70%) also significantly increased, whereas L-selectin (CD62L, -70%) decreas ed. The effects of LCT/MCT were mimicked by the MCT emulsion. ICAM-1 adhesi on (% beads bound) was increased by LCT/MCT (34% +/- 4%), whereas LCT (19% +/- 3%) and SL (20% +/- 2%) had no effect compared with medium (17% +/- 3%) . Conclusions: LCT/MCT and MCT, contrary to LCT and SL emulsions, increased neutrophil beta(2) integrin expression, adhesion, and degranulation. Apart from other emulsion constituents, triglyceride chain length might there fo re be a key feature in the interaction of lipid Emulsions and the phagocyte immune system.