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...

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These results suggest that TNF-alpha enhances in vitro vascular calcification by promoting osteoblastic differentiation of vascular cells through the cAMP pathway.

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Abstract-An early event in acute and chronic inflammation and associated diseases such as atherosclerosis and rheumatoid arthritis is the induced expression of specific adhesion molecules on the surface of endothelial cells (ECs), which subsequently bind leukocytes. Peroxisome proliferator-activated receptors (PPARs), members of the nuclear receptor superfamily of transcription factors, are activated by fatty acid metabolites, peroxisome proliferators, and thiazolidinediones and are now recognized as important mediators in the inflammatory response. Whether PPAR activators influence the inflammatory responses of ECs is unknown. We show that the PPAR activators 15-deoxy-⌬ 12,14 -prostaglandin J 2 (15d-PGJ 2 ), Wyeth 14643, ciglitazone, and troglitazone, but not BRL 49653, partially inhibit the induced expression of vascular cell adhesion molecule-1 (VCAM-1), as measured by ELISA, and monocyte binding to human aortic endothelial cells (HAECs) activated by phorbol 12-myristate 13-acetate (PMA) or lipopolysaccharide. The "natural" PPAR activator 15d-PGJ 2 had the greatest potency and was the only tested molecule capable of partially inhibiting the induced expression of E-selectin and neutrophil-like HL60 cell binding to PMA-activated HAECs. Intracellular adhesion molecule-1 induction by PMA was unaffected by any of the molecules tested. Both PPAR-␣ and PPAR-␥ mRNAs were detected in HAECs by using reverse transcription-polymerase chain reaction and a ribonuclease protection assay; however, we have yet to determine which, if any, of the PPARs are mediating this process. These results suggest that certain PPAR activators may help limit chronic inflammation mediated by VCAM-1 and monocytes without affecting acute inflammation mediated by E-selectin and neutrophil binding.