Oxidized LDL induce hsp70 expression in human smooth muscle cells.

Heat shock protein 70 (hsp70) has been detected in atherosclerotic lesions, in which endothelial cells and smooth muscle cells are involved. In a previous report we showed that Ox-LDL, a causal factor in atherosclerosis, could induce hsp70 expression in cultured human endothelial cells [Zhu et al. B.B.R.C. 1994, 200:389]. Here, with immunofluorescence and immunoblotting techniques, we show that Ox-LDL are capable of inducing hsp70 expression also in human smooth muscle cells, and that this induction is dependent on cell density and on the concentration of Ox-LDL. The induced expression of hsp70 was higher in human umbilical vein smooth muscle cells than in a human smooth muscle cell line. Conversely, Ox-LDL was cytotoxic to both types of cells, more so to the human smooth muscle cell line. These observations indicate that Ox-LDL may be a stress responsible for hsp70 expression in atherosclerotic plaques and the presence of hsp70 in plaques may be a useful marker for continuous oxidative damage in the arterial wall.