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Antiproliferative activity to glomerular mesangial cells and receptor binding of a heparin-mimicking polyaromatic
A Katz1, I Vlodavsky, M Davies
1Department of Oncology, Hadassah-Hebrew University Hospital, Jerusalem, Israel.
Abstract:
Proliferation of mesangial cells (MC) is a key feature in the pathogenesis of numerous renal diseases involving the glomerulus. Heparin, one of several compounds capable of suppressing MC proliferation, did not prove beneficial in the treatment of human glomerular diseases. In a search for a superior antiproliferative agent, a synthetic polyaromatic "heparin mimicking" compound (RG-13577, polymer of 4-hydroxyphenoxy acetic acid, M(r) approximately 5800), previously reported to inhibit the proliferation of vascular smooth muscle cells, was applied. RG-13577 exhibits approximately 1% of the anticoagulant activity of heparin and is nontoxic in animal experiments. Proliferation of primary rat MC was almost completely inhibited in the presence of 10 to 25 micrograms/ml RG-13577, and 50% inhibition was obtained at 1 to 5 micrograms/ml RG-13577. The cells resumed their normal growth rate after removal of RG-13577 from the culture medium. Under the same conditions, heparin exerted only a small inhibitors effect. RG-13577 inhibited signaling (i.e., tyrosine phosphorylation) and MC proliferation induced by both basic fibroblast growth factor and platelet-derived growth factor. RG-13577 binds to a naturally produced extracellular matrix, and the bound molecule retained its antiproliferative effect toward MC. 14C-Labeled RG-13577 also binds to cultured MC in a specific and saturable manner. Binding of 14C-RG-13577 was reduced by 80 to 90% in the presence of excess unlabeled RG-13577, apolipoprotein E, or lactoferrin, but there was no effect with heparin. Furthermore, the antiproliferative effect of RG-13577 was abolished in the presence of lactoferrin. It is proposed that compound RG-13577 inhibits MC proliferation through neutralization of growth-promoting factors, primarily heparin-binding growth factors, and possibly through binding to specific cell surface receptors, most likely the LDL receptor-related protein. RG-13577 and related polyanionic compounds may be applied to inhibit MC proliferation in glomerular diseases.
Insights
A novel synthetic compound, RG-13577, effectively inhibits mesangial cell proliferation, a key factor in kidney diseases. This heparin-mimicking agent shows promise as a therapeutic for glomerular diseases.
Area of Science:
- Nephrology
- Cell Biology
- Pharmacology
Background:
- Mesangial cell (MC) proliferation is central to glomerular disease pathogenesis.
- Heparin, though a known suppressor of MC proliferation, has limited clinical benefit in human glomerular diseases.
- A need exists for more effective antiproliferative agents for glomerular diseases.
Purpose of the Study:
- To evaluate the antiproliferative efficacy of a synthetic heparin-mimicking compound, RG-13577, on mesangial cells.
- To investigate the mechanism of action of RG-13577 in inhibiting mesangial cell proliferation.
- To compare the efficacy of RG-13577 with heparin in suppressing mesangial cell proliferation.
Main Methods:
- Primary rat mesangial cells were cultured and treated with varying concentrations of RG-13577 and heparin.
- Cell proliferation was assessed, and the effect of RG-13577 on growth factor-induced signaling (tyrosine phosphorylation) was examined.
- Binding studies were performed using 14C-labeled RG-13577 to assess its interaction with extracellular matrix and cell surface receptors, including competition assays with other molecules like apolipoprotein E and lactoferrin.
Main Results:
- RG-13577 demonstrated potent inhibition of mesangial cell proliferation, with significant effects at 1-25 µg/ml, far exceeding heparin's inhibitory capacity.
- RG-13577 effectively blocked proliferation induced by basic fibroblast growth factor and platelet-derived growth factor by inhibiting associated tyrosine phosphorylation.
- RG-13577 exhibited specific, saturable binding to mesangial cells and extracellular matrix, with competition observed for apolipoprotein E and lactoferrin, but not heparin. Lactoferrin abolished RG-13577's antiproliferative effect.
Conclusions:
- RG-13577 is a potent inhibitor of mesangial cell proliferation, acting through mechanisms distinct from heparin.
- The compound likely neutralizes heparin-binding growth factors and may interact with cell surface receptors like the LDL receptor-related protein.
- RG-13577 and related polyanionic compounds represent a potential therapeutic strategy for managing glomerular diseases characterized by mesangial cell proliferation.