Human neutrophil membrane fluidity after exposure to structurally different lipid emulsions.
BACKGROUND
We have previously reported that medium-chain triglyceride (MCT)-containing lipid emulsions, contrary to long-chain triglyceride (LCT) emulsions, activate human neutrophils. This activation might result from functional alterations in cellular membranes induced by MCT. Membrane fluidity is such a feature with known clinical implications and can be assessed by fluorescence polarization measurements. This study was performed to investigate whether exposure to various emulsions distinctively influences neutrophil membrane fluidity.


METHODS
Neutrophils from 8 volunteers were incubated in medium or physiologic 2.5 mmol/L emulsions containing LCT, mixed LCT/MCT, or structured lipids (SL). Subsequently, the cells were washed and anisotropy, ie, the reciprocal of fluidity, was measured using the fluorescent probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and trimethyl-ammonium (TMA)-DPH.


RESULTS
Compared with nonlipid-exposed neutrophils, LCT/MCT and, to a lesser degree, SL decreased fluorescence anisotropy and thus increased membrane fluidity, which was measured by DPH anisotropy, whereas LCT had no effect. Similar results were obtained with the more polar probe TMA-DPH.


CONCLUSIONS
These data suggest that the neutrophil-activating effect of MCT-containing emulsions may, at least in part, be mediated by an effect on cellular membrane fluidity.
Wanten
G J
GJ
Department of Gastroenterology and Hepatology, University Medical Center Nijmegen, The Netherlands. G.Wanten@gastro.azn.nl
Naber
A H
AH
D000328:Adult; D002478:Cells, Cultured; D005217:Fat Emulsions, Intravenous / Q000737:chemistry* / Q000494:pharmacology; D005227:Fatty Acids / Q000737:chemistry* / Q000494:pharmacology; D005260:Female; D005454:Fluorescence Polarization; D006801:Humans; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects* / Q000502:physiology; D009504:Neutrophils / Q000187:drug effects* / Q000502:physiology
D005217:Fat Emulsions, Intravenous; D005227:Fatty Acids