Liposomes composed of unsaturated lipids for membrane modification of human erythrocytes

Abstract

Previous studies have shown that certain saturated lipids protect red blood cells (RBCs) during hypothermic storage but provide little protection during freezing or freeze-drying, whereas various unsaturated lipids destabilize RBCs during hypothermic storage but protect during freezing and freeze-drying. The protective effect of liposomes has been attributed to membrane modifications. We have previously shown that cholesterol exchange and lipid transfer between liposomes composed of saturated lipids and RBCs critically depends on the length of the lipid acyl chains. In this study the effect of unsaturated lipids with differences in their number of unsaturated bonds (18:0/18:1, 18:1/18:1, 18:2/18:2) on RBC membrane properties has been studied. RBCs were incubated in the presence of liposomes and both the liposomal and RBC fraction were analyzed by Fourier transform infrared spectroscopy (FTIR) after incubation. The liposomes caused an increase in RBC membrane conformational disorder at suprazero temperatures. The fluidizing effect of the liposomes on the RBC membranes, however, was found to be similar for the different lipids irrespective of their unsaturation level. The gel to liquid crystalline phase transition temperature of the liposomes increased after incubation with RBCs. RBC membrane fluidity increased linearly during the first 8 hours of incubation in the presence of liposomes. The increase in RBC membrane fluidity was found to be temperature dependent and displayed Arrhenius behaviour between 20 and 40°C, with an activation energy of 88 kJ mol^-1. Taken together, liposomes composed of unsaturated lipids increase RBC membrane conformational disorder, which could explain their cryoprotective action.

Keywords::

• Fourier transform infrared spectroscopy
• lipid phase behaviour
• liposomes
• erythrocytes
• membrane modification

Acknowledgements

We kindly acknowledge Dr Heuft from the Hanover Medical school blood donation service for providing blood samples for the experiments. This work is supported by funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) for the Cluster of Excellence REBIRTH (From Regenerative Biology to Reconstructive Therapy) and from a grant “Liposomes in Transfusion Medicine: An Approach for Reducing the Red Blood Cell Hypothermic Storage Lesion” to JA from the Canadian Blood Services/Canadian Institutes for Health Research.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.