This proposal aims to provide a fundamental understanding of cholesterol crystal nucleation from biliary vesicles and plasma lipoproteins in the context of gallstone disease and atherosclerosis, respectively. Cholesterol crystals are precursors to gallstones; inhibiting cholesterol nucleation offers a potential means of preventing stones. Crystals are also considered to be hallmarks of advanced atherosclerotic plaques, which typically become life-threatening only after rupture, followed by thrombosis and occlusion of an artery. Given that plaque stability correlates with the presence of crystals, inhibiting cholesterol nucleation offers a potential means of maintaining stability of atherosclerotic lesions and protecting against myocardial infarction. Development of preventive, clinical strategies based on inhibiting cholesterol nucleation requires a fundamental understanding of the nucleation mechanism. Molecular details concerning cholesterol nucleation are lacking, both in blood and in bile. However, recent work has shed important new insights, and kinetic and mechanistic studies of cholesterol nucleation are now feasible. This proposal is designed to test the hypotheses that 1) nanodomains of laterally phase-separated cholesterol constitute an equilibrium phase within lipid membranes; these nanondomains are distinct from cholesterol-rich domains and rafts 2) cholesterol nanodomains can act as crystal nucleation sites in non-equilibrium (i.e., in vivo) systems, and 3) aggregation of either vesicles or low density lipoproteins (LDL) facilitates collisions of cholesterol nanodomains in adjacent membranes; whereas aggregation alone is sufficient to induce nucleation from vesicles, nucleation from LDL requires uptake by macrophages.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM071355-03
Application #
7176052
Study Section
Hepatobiliary Pathophysiology Study Section (HBPP)
Program Officer
Chin, Jean
Project Start
2005-02-01
Project End
2010-01-31
Budget Start
2007-02-01
Budget End
2008-01-31
Support Year
3
Fiscal Year
2007
Total Cost
$197,554
Indirect Cost
Name
Drexel University
Department
Engineering (All Types)
Type
Schools of Engineering
DUNS #
002604817
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Brown, Angela C; Wrenn, Steven P (2013) Nanoscale phase separation in DSPC-cholesterol systems. Langmuir 29:9832-40
Walters, Michael J; Wrenn, Steven P (2011) Mechanistic roles of lipoprotein lipase and sphingomyelinase in low density lipoprotein aggregation. J Colloid Interface Sci 363:268-74
Walters, Michael J; Wrenn, Steven P (2010) Size-selective uptake of colloidal low density lipoprotein aggregates by cultured white blood cells. J Colloid Interface Sci 350:494-501
Walters, Michael J; Wrenn, Steven P (2008) Effect of sphingomyelinase-mediated generation of ceramide on aggregation of low-density lipoprotein. Langmuir 24:9642-7
Brown, Angela C; Towles, Kevin B; Wrenn, Steven P (2007) Measuring raft size as a function of membrane composition in PC-based systems: Part II--ternary systems. Langmuir 23:11188-96
Brown, Angela C; Towles, Kevin B; Wrenn, Steven P (2007) Measuring raft size as a function of membrane composition in PC-based systems: Part 1--binary systems. Langmuir 23:11180-7
Towles, Kevin B; Brown, Angela C; Wrenn, Steven P et al. (2007) Effect of membrane microheterogeneity and domain size on fluorescence resonance energy transfer. Biophys J 93:655-67
Guarino, Andrew J; Lee, Sum P; Wrenn, Steven P (2006) Interactions between sphingomyelin and cholesterol in low density lipoproteins and model membranes. J Colloid Interface Sci 293:203-12
Guarino, Andrew J; Tulenko, Thomas N; Wrenn, Steven P (2006) Sphingomyelinase-to-LDL molar ratio determines low density lipoprotein aggregation size: biological significance. Chem Phys Lipids 142:33-42