Saha Amit K, Osmulski Pawel, Dallo Shatha F, Gaczynska Maria, Huang Tim H-M, Ramasubramanian Anand K
Department of Biomedical Engineering, The University of Texas at San Antonio, San Antonio, Texas.
Department of Molecular Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas.
Biophys J. 2017 Apr 11;112(7):1481-1488. doi: 10.1016/j.bpj.2017.02.021.
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/cm 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.
胆固醇是动脉粥样硬化的一个重要风险因素，因为单核细胞/巨噬细胞会主动摄取胆固醇。单核细胞从流动血液中募集到动脉粥样硬化病灶是动脉粥样硬化发展过程中的关键第一步。胆固醇含量会改变细胞膜硬度以及横向脂质和蛋白质扩散。我们推测胆固醇含量会通过改变黏附受体的动力学来调节单核细胞向炎症内皮表面的募集。我们使用甲基-β-环糊精在新鲜分离的人单核细胞中降低或增加细胞胆固醇水平。我们研究了这些变化对微通道中单核细胞在1达因/厘米的E-选择素表面滚动力学的影响。使用成像流式细胞术和原子力显微镜，我们表征了脂筏和单核细胞表面E-选择素反受体CD44的分布。我们观察到较低的胆固醇水平导致单核细胞在E-选择素包被表面上由CD44介导的均匀滚动。我们还观察到胆固醇耗尽的细胞具有更高的膜流动性，以及CD44反受体更均匀的分布，与胆固醇富集的细胞相比，这导致细胞运动更平滑。这项工作表明胆固醇可以通过调节受体流动性来调节单核细胞黏附，我们的结果为炎症的生物物理调节提供了见解，以便更好地理解动脉粥样硬化和高胆固醇血症等疾病。
