Variability of cholesterol accessibility in human red blood cells measured using a bacterial cholesterol-binding toxin.
Cholesterol partitions into accessible and sequestered pools in cell membranes. Here, we describe a new assay using fluorescently-tagged anthrolysin O, a cholesterol-binding bacterial toxin, to measure accessible cholesterol in human red blood cells (RBCs). Accessible cholesterol levels were stable within individuals, but varied >10 fold among individuals. Significant variation was observed among ethnic groups (Blacks>Hispanics>Whites). Variation in accessibility of RBC cholesterol was unrelated to the cholesterol content of RBCs or plasma, but was associated with the phospholipid composition of the RBC membranes and with plasma triglyceride levels. Pronase treatment of RBCs only modestly altered cholesterol accessibility. Individuals on hemodialysis, who have an unexplained increase in atherosclerotic risk, had significantly higher RBC cholesterol accessibility. Our data indicate that RBC accessible cholesterol is a stable phenotype with significant inter-individual variability. Factors both intrinsic and extrinsic to the RBC contribute to variation in its accessibility. This assay provides a new tool to assess cholesterol homeostasis among tissues in humans.
Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States.
Rima S
RS
Chakrabarti
Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States.
Sally A
SA
Ingham
Departments of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, United States.
Julia
J
Kozlitina
Departments of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, United States.
Austin
A
Gay
Departments of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, United States.
Jonathan C
JC
Cohen
Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.
Arun
0000-0002-7266-7336
A
Radhakrishnan
Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States.|Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.
Helen H
0000-0002-8700-9897
HH
Hobbs
D000293:Adolescent; D000328:Adult; D001426:Bacterial Proteins / Q000378:metabolism*; D002784:Cholesterol / Q000032:analysis*; D004912:Erythrocytes / Q000737:chemistry*; D005006:Ethnicity; D005260:Female; D005470:Fluorometry; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008875:Middle Aged; D011485:Protein Binding; D055815:Young Adult
D001426:Bacterial Proteins; D008562:Membrane Glycoproteins; C498000:anthrolysin O, Bacillus anthracis; D002784:Cholesterol
biochemistry; cholesterol; human; human biology; medicine; membranes; red blood cells; reverse cholesterol transport