Guha Madhumita, Gursky Olga
Department of Physiology and Biophysics, School of Medicine, Boston University, Boston, MA 02118, USA.
J Lipids. 2011;2011:493720. doi: 10.1155/2011/493720. Epub 2011 May 15.
Very low-density lipoproteins (VLDL) are precursors of low-density lipoproteins (LDL, or "bad cholesterol"). Factors affecting structural integrity of VLDL are important for their metabolism. To assess the role of electrostatic interactions in VLDL stability, we determined how solvent ionic conditions affect the heat-induced VLDL remodeling. This remodeling involves VLDL fusion, rupture, and fission of apolipoprotein E-containing high-density lipoprotein-(HDL-) like particles similar to those formed during VLDL-to-LDL maturation. Circular dichroism and turbidity show that increasing sodium salt concentration in millimolar range reduces VLDL stability and its enthalpic component. Consequently, favorable electrostatic interactions stabilize VLDL. Reduction in pH from 7.4 to 6.0 reduces VLDL stability, with further destabilization detected at pH < 6, which probably results from titration of the N-terminal α-amino groups and free fatty acids. This destabilization is expected to facilitate endosomal degradation of VLDL, promote their coalescence into lipid droplets in atherosclerotic plaques, and affect their potential use as drug carriers.
极低密度脂蛋白(VLDL)是低密度脂蛋白(LDL,即“坏胆固醇”)的前体。影响VLDL结构完整性的因素对其代谢很重要。为了评估静电相互作用在VLDL稳定性中的作用,我们确定了溶剂离子条件如何影响热诱导的VLDL重塑。这种重塑涉及VLDL融合、破裂以及类似于VLDL向LDL成熟过程中形成的含载脂蛋白E的高密度脂蛋白(HDL)样颗粒的裂变。圆二色性和浊度表明,在毫摩尔范围内增加钠盐浓度会降低VLDL稳定性及其焓成分。因此,有利的静电相互作用可稳定VLDL。pH从7.4降至6.0会降低VLDL稳定性,在pH < 6时检测到进一步的不稳定,这可能是由于N端α-氨基和游离脂肪酸的滴定所致。这种不稳定预计会促进VLDL的内体降解,促进它们在动脉粥样硬化斑块中聚集成脂滴,并影响它们作为药物载体的潜在用途。