Tani N
Research Institute, Kaneka Corporation, Hyogo, Japan.
Artif Organs. 1996 Aug;20(8):922-9. doi: 10.1111/j.1525-1594.1996.tb04571.x.
Low-density lipoprotein (LDL) is widely recognized as one of the major risk factors for developing coronary heart diseases. Despite intensive development of LDL-lowering drugs, there still exist those patients with refractory hyperlipidemia whose plasma LDL levels are not sufficiently lowered by drugs. LDL apheresis, direct removal of plasma LDL from circulating blood, is thought to be the most promising treatment for such refractory patients. Various techniques, such as the use of an immunoadsorbent utilizing an anti-LDL antibody, have been used in an attempt to achieve the selective removal of LDL. However, none were widely used because of complications, poor selectivity, and so forth. To establish a safe and effective LDL apheresis system, we chose a synthetic affinity adsorbent as the LDL-removing device. Synthetic polyanion compounds were used as the affinity ligands for LDL adsorbent to simulate the anion-rich sequence of LDL binding sites in the human LDL receptor. Among various polyanion compounds, those polyanions with sulfate or sulfonate groups and hydrophilic backbone were found to have strong affinity for LDL. In contrast, polyanions with carboxyl groups showed poor affinity. Dextran sulfate (DS) was selected as the affinity ligand of LDL adsorbent for its high affinity and low toxicity. The influence of its charge density and molecular weight on its affinity for LDL was suitable. The affinity rapidly increased as the charge density increased, then, reached a constant value. Little affinity was found for either the DS monomer (glucose sulfate) or DS with a molecular weight higher than 10(4) daltons whereas DS with molecular weights in the midrange showed strong affinity. DS with a midrange molecular weight was immobilized on cellulose hard gel to give LDL adsorbent clinical application. The adsorbent demonstrated an excellent selectivity for LDL and very low density lipoprotein (VLDL) in vitro. Adsorption of high-density lipoprotein and major plasma proteins was almost negligible. Additional study of the LDL-binding mechanism revealed that DS directly interacts with positively charged sites on LDL, which demonstrates that the nature of the interaction is the same as that of LDL receptor. An LDL adsorption column (Liposorber) packed with an LDL adsorbent and polysulfone hollow-fiber plasma separator (Sulflux) was developed as an efficient LDL apheresis system. Clinical investigation proved that this system is capable of intensively lowering the plasma LDL level without affecting major plasma components.
低密度脂蛋白（LDL）被广泛认为是引发冠心病的主要危险因素之一。尽管降低LDL的药物得到了深入研发，但仍有一些难治性高脂血症患者，其血浆LDL水平无法通过药物充分降低。LDL单采术，即从循环血液中直接去除血浆LDL，被认为是治疗此类难治性患者最有前景的方法。为了实现LDL的选择性去除，人们尝试了各种技术，例如使用利用抗LDL抗体的免疫吸附剂。然而，由于并发症、选择性差等原因，这些技术都没有得到广泛应用。为了建立一个安全有效的LDL单采系统，我们选择了一种合成亲和吸附剂作为LDL去除装置。合成聚阴离子化合物被用作LDL吸附剂的亲和配体，以模拟人LDL受体中富含阴离子的LDL结合位点序列。在各种聚阴离子化合物中，发现那些带有硫酸根或磺酸根基团以及亲水性主链的聚阴离子对LDL具有很强的亲和力。相比之下，带有羧基的聚阴离子显示出较差的亲和力。硫酸葡聚糖（DS）因其高亲和力和低毒性被选为LDL吸附剂的亲和配体。其电荷密度和分子量对其与LDL亲和力的影响是合适的。随着电荷密度的增加，亲和力迅速增加，然后达到一个恒定值。对于DS单体（葡萄糖硫酸盐）或分子量高于10⁴道尔顿的DS几乎没有发现亲和力，而中等分子量的DS显示出很强的亲和力。将中等分子量的DS固定在纤维素硬凝胶上，以便LDL吸附剂能够应用于临床。该吸附剂在体外对LDL和极低密度脂蛋白（VLDL）表现出优异的选择性。对高密度脂蛋白和主要血浆蛋白的吸附几乎可以忽略不计。对LDL结合机制的进一步研究表明，DS直接与LDL上带正电的位点相互作用，这表明这种相互作用的性质与LDL受体相同。一种装有LDL吸附剂的LDL吸附柱（Liposorber）和聚砜中空纤维血浆分离器（Sulflux）被开发为一种高效的LDL单采系统。临床研究证明，该系统能够在不影响主要血浆成分的情况下大幅降低血浆LDL水平。
