A synthetic heparin-mimicking polyanionic compound binds to the LDL receptor-related protein and inhibits vascular smooth muscle cell proliferation

Abstract

A synthetic heparin-mimicking polyaromatic anionic compound RG-13577 (polymer of 4-hydroxyphenoxy acetic acid and formaldehyde ammonium salt, Mr approximately 5800) exhibits specific binding to vascular smooth muscle cells (SMCs) and inhibits their proliferative response to growth promoting factors. Receptor binding of (14)C-RG-13577 was efficiently competed by apolipoprotein E3 (apoE), lactoferrin, and the LRP (LDL receptor-related protein) receptor associated 39 kDa protein (RAP). Unlike cell surface binding of apoE, binding of RG-13577 to SMCs was not affected by heparin, heparan sulfate degrading enzymes, or low density lipoprotein (LDL). Moreover, wild-type and heparan sulfate-deficient Chinese hamster ovary (CHO) cells, as well as normal- and LDL receptor negative- human skin fibroblasts bind RG-13577, but not apoE, to a similar extent. On the other hand, homozygous mouse embryonic fibroblasts deficient in the LDL receptor-related protein (LRP) expressed a markedly reduced binding of RG-13577 as compared to normal mouse embryonic fibroblasts. These results indicate that RG-13577 and related compounds bind to the LRP receptor on the surface of vascular SMCs. Addition of lactoferrin to cultured SMCs protected the cells against the antiproliferative effect of compound RG-13577, suggesting that this inhibition is mediated by RG-13577 binding to LRP receptors on the SMC surface. Altogether, we have identified a series of synthetic polyaromatic anionic molecules that exhibit specific binding to LRP and thereby exert an antiproliferative effect on vascular SMCs. These compounds are applied to suppress SMC proliferation associated with restenosis and accelerated atherosclerosis.

Kallistatin antagonizes Wnt/β-catenin signaling and cancer cell motility via binding to low-density lipoprotein receptor-related protein 6

“…Kallistatin, but not its heparin mutant, was also demonstrated to suppress VEGF-induced proliferation, migration and permeability in endothelial cells [11]. Studies have indicated that LRP binds to a synthetic heparin-mimicking compound on the surface of vascular smooth muscle cells [28] and functions as a heparin-dependent adhesion receptor for connective tissue growth factor in hepatic cells [29]. Therefore, it is likely that kallistatin binds to LRP6 via its heparin-binding site.…”

Heparin-Mimicking Polymers: Synthesis and Biological Applications

“…Interestingly, the authors found that when up to 1 μg/mL of RG-13577 was incubated in the presence of 20 ng/mL of heparin, increased binding of FGF2 to its receptor was observed. Even though RG-13577 has received attention for its inhibitory activity in cells that cause angiogenesis, arteriosclerosis, glomerulosclerosis, and spinal chord inflammation, − this last data at lower concentrations suggested that RG-13577 could be further investigated as candidate for regenerative therapy in combination with heparin.…”