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Cholesterol Regulates Monocyte Rolling through CD44 Distribution
Amit K Saha1, Pawel Osmulski2, Shatha F Dallo1
1Department of Biomedical Engineering, The University of Texas at San Antonio, San Antonio, Texas.
Insights
Cholesterol levels impact monocyte adhesion to inflamed surfaces. Lowering cholesterol enhances monocyte rolling by increasing membrane fluidity and receptor distribution, offering insights into atherosclerosis.
Area of Science:
- Biophysics
- Cell Biology
- Immunology
Background:
- Cholesterol is a key risk factor for atherosclerosis, influencing monocyte/macrophage uptake.
- Monocyte recruitment to atherosclerotic lesions is a critical initial step in disease development.
- Cellular cholesterol affects membrane properties like stiffness and receptor diffusion.
Purpose of the Study:
- To investigate how cellular cholesterol content modulates monocyte recruitment to inflamed endothelium.
- To explore the role of cholesterol in altering adhesion receptor dynamics during monocyte rolling.
Main Methods:
- Human monocytes were depleted or enriched for cholesterol using methyl-β-cyclodextran.
- Monocyte rolling mechanics on E-selectin surfaces were studied in microchannels at 1 dyn/cm².
- Imaging flow cytometry and atomic force microscopy assessed lipid rafts and CD44 distribution.
Main Results:
- Reduced cholesterol led to uniform, CD44-mediated monocyte rolling on E-selectin.
- Cholesterol-depleted monocytes exhibited increased membrane fluidity and more even CD44 distribution.
- This resulted in smoother monocyte motion compared to cholesterol-enriched cells.
Conclusions:
- Cholesterol content regulates monocyte adhesion by controlling receptor mobility.
- Findings provide biophysical insights into inflammation and diseases like atherosclerosis and hypercholesterolemia.
Abstract:
Cholesterol is an important risk factor of atherosclerosis, due to its active uptake by monocytes/macrophages. Monocyte recruitment from flowing blood to atherosclerotic foci is the key first step in the development of atherosclerosis. Cholesterol content alters cell membrane stiffness, and lateral lipid and protein diffusion. We hypothesized that cholesterol content will modulate the recruitment of monocytes to inflamed endothelial surface by altering the dynamics of adhesion receptors. We depleted or enriched the cellular cholesterol levels using methyl-β-cyclodextran in freshly isolated human monocytes. We investigated the effect of these changes on the mechanics of monocyte rolling on E-selectin surfaces at 1 dyn/cm2 in microchannels. Using imaging flow cytometry and atomic force microscopy, we characterized the distribution of lipid rafts and the E-selectin counterreceptor CD44 on the monocyte surface. We observed that lower levels of cholesterol resulted in the uniform, CD44-mediated rolling of monocytes on the E-selectin-coated surfaces. We also observed that cells depleted of cholesterol had higher membrane fluidity, and more uniform distribution of CD44 counterreceptor, which resulted in smooth motion of the cells compared to cells enriched with cholesterol. This work demonstrates that cholesterol can modulate monocyte adhesion by regulating the receptor mobility, and our results provide insights into the biophysical regulation of inflammation for the better understanding of diseases like atherosclerosis and hypercholesterolemia.