Submitted on February 23, 2006
Revised on October 25, 2006
Accepted on October 25, 2006
High density lipoprotein subfractions: isolation, composition and their duplicitous role in oxidation
Peter A. C. McPherson, Ian S. Young, Bronac McKibben, and Jane McEneny
Nutrition and Metabolism Group, Queen's University Belfast, Belfast, County Antrim BT12 6BJ
Corresponding Author: j.mceneny{at}qub.ac.uk
The plasma HDLs are a major class of cholesterol transporting lipoprotein which can be divided into two distinct subfractions, HDL2 and HDL3, by ultracentrifugation. Existing methods for the subfractionation of HDL requires lengthy ultracentrifugations, making them unappealing for large scale studies. We describe a method which subfractionates HDL from plasma in only 6 hours, representing a substantial decrease in total isolation time. The subfractions so isolated were assessed for a variety of lipid and protein components, in addition to their susceptibility to oxidation, both alone and in combination with VLDL and LDL. We report for the first time a pro-oxidant role for HDL during VLDL oxidation, where HDL is donating preformed hydroperoxides to VLDL in a CETP-dependent process. Examination of the participation of HDL in LDL oxidation has reinforced its classic role as a potent antioxidant. Furthermore, we have also implicated the second major HDL-associated enzyme LCAT in these processes, whereby it acts as a potent pro-oxidant during VLDL oxidation, but as an antioxidant during LDL oxidation. Thus, we have identified a potentially duplicitous role for HDL in the pathogenesis of atherosclerosis, due to both CETP and LCAT.
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