Inhibition of human endothelial cell proliferation by gold compounds

Neovascularization has a role in the propagation of rheumatoid synovitis because the spread of mononuclear cell infiltration and the growth of pannus are dependent on the growth of new blood vessels. Growth of such vessels requires local endothelial cell (EC) proliferation. Inhibition of synovial EC proliferation, therefore, would have the potential to diminish rheumatoid inflammation. We have, therefore, studied the effects of gold sodium thiomalate (GST), auranofin, and gold chloride on the proliferation of human umbilical vein EC. GST suppressed both basal and EC growth factor-induced tritiated thymidine incorporation into EC in a dose-dependent fashion. Inhibition was observed with concentrations as low as 1 microgram/ml GST, 5 micrograms/ml gold chloride, and 0.1 microgram/ml auranofin, levels attainable in blood and synovium of patients. These results suggest that gold compounds have an antiangiogenic effect. The low concentrations inhibiting EC proliferation suggest that gold compounds may suppress rheumatoid synovitis by reducing the number of small blood vessels available for mononuclear cell infiltration and synovial tissue proliferation.