After exposure to low density lipoprotein (LDL) that had been minimally modified by oxidation (MM-LDL), human endothelial cells (EC) and smooth muscle cells (SMC) cultured separately or together produced 2-to 3-fold more monocyte chemotactic activity than did control cells or cells exposed to freshly isolated LDL. This increase in monocyte chemotactic activity was paralleled by increases in mRNA levels for a monocyte chemotactic protein 1 (MCP-1) that is constitutively produced by the human glioma U-105MG cell line. Antibody that had been prepared against cultured baboon smooth muscle cell chemotactic factor (anti-SMCF) did not inhibit monocyte migration induced by the potent bacterial chemotactic factor f-Met-Leu-Phe. However, anti-SMCF completely inhibited the monocyte chemotactic activity found in the media of U-1O5MG cells, EC, and SMC before and after exposure to MM-LDL. Moreover, monocyte migration into the subendothelial space of a coculture of EC and SMC that had been exposed to MM-LDL was completely inhibited by anti-SMCF. Anti-SMCF specifically immunoprecipitated 10-kDa and 12.5-kDa proteins from EC. Incorporation of [35Slmethi-onine into the immunoprecipitated proteins paralleled the monocyte chemotactic activity found in the medium of MM-LDL stimulated EC and the levels of MCP-1 mRNA found in the EC. We conclude that (g) SMCF is in fact MCP-1 and (it) MCP-1 is induced by MM-LDL.An important early event in atherogenesis is an increased recruitment of monocytes into the arterial subendothelium (1)(2)(3)(4). Previous studies have shown that endothelial cells (EC) (5, 6) and smooth muscle cells (SMC) (7,8) in culture constitutively produce a chemotactic factor that acts on monocytes but not neutrophils. Graves and colleagues (9) demonstrated that the monocyte chemotactic activity in the supernatants from a number of tumor cell lines was inhibited by an antibody made against baboon smooth muscle cell chemotactic factor (anti-SMCF) (10). Additionally they demonstrated a strong concordance with immunoprecipitation of a protein with an apparent molecular mass of 14.4 kDa. A human glioma cell line, U-1OSMG, constitutively expresses monocyte chemotactic activity. The protein responsible for this activity has been purified, sequenced, and named monocyte chemotactic protein 1 (MCP-1) (11, 12). Graves and colleagues did not test their antibody against the chemotactic activity secreted by the U-1O5MG cell line, but based on limited primary sequence data from the baboon smooth muscle chemotactic protein, they concluded that their protein was homologous to MCP-1.We have recently demonstrated that low density lipoprotein (LDL) that has been minimally modified (MM-LDL) is indistinguishable from native LDL by the LDL receptor, is not recognized by the scavenger receptor, and induces EC to secrete high levels of monocyte chemotactic activity, whereas native LDL does not (13). We have also shown that MM-LDL induces EC to produce colony-stimulating factors, including monocyte colony-stimulating factor (M-CSF), w...

Background-Low endothelial shear stress (ESS) promotes the development of atherosclerosis; however, its role in the progression of atherosclerotic plaques and evolution to inflamed high-risk plaques has not been studied. Our hypothesis was that the lowest values of ESS are responsible for the development of high-risk coronary atherosclerotic plaques associated with excessive expansive remodeling. Methods and Results-Twenty-four swine, treated with streptozotocin to induce diabetes and fed a high-fat diet, were allocated into early (nϭ12) and late (nϭ12) atherosclerosis groups. Intima-media thickness was assessed by intravascular ultrasound in the coronary arteries at weeks 4 and 8 in the early group and weeks 23 and 30 in the late group. Plaques started to develop after week 8, leading to marked heterogeneity in plaque severity at week 30. ESS was calculated in plaque-free subsegments of interest (nϭ142) in the late group at week 23. Coronary arteries (nϭ31) of this group were harvested at week 30, and the subsegments of interest were identified and analyzed histopathologically. Low ESS was an independent predictor of the development of high-risk plaques, characterized by intense lipid accumulation, inflammation, thin fibrous cap, severe internal elastic lamina degradation, and excessive expansive remodeling. The severity of high-risk plaque characteristics at week 30 was significantly correlated with the magnitude of low ESS at week 23. Conclusions-The