Tissue factor induction by aggregated LDL depends on LDL receptor-related protein expression (LRP1) and Rho A translocation in human vascular smooth muscle cells.
OBJECTIVE
Low density lipoprotein (LDL) internalized in the vascular wall and modified by binding to extracellular matrix-proteoglycans (ECM) becomes aggregated (agLDL). AgLDL induces tissue factor (TF) expression and activity in human vascular smooth muscle cells (VSMC). TF expression in vascular cells promotes the prothrombotic transformation of the vascular wall. However, the mechanisms by which agLDL induces TF are not known. The aim of this study was to investigate the mechanisms involved in TF activation by extracellular matrix-modified LDL in human VSMC.


RESULTS
AgLDL significantly induces TF expression (real time PCR and Western blot analysis) and procoagulant activity (factor Xa generation test) in human VSMC. HMG-CoA reductase inhibition completely prevents agLDL-induced TF expression and partially inhibits agLDL-TF activation. These effects are reverted by geranylgeranyl pyrophosphate (GGPP) but not by farnesyl pyrophosphate (FPP), suggesting the involvement of a geranylated protein in agLDL-TF induction. AgLDL increases Rho A translocation (2-fold) from the cytoplasm to the cell membrane in control but not in simvastatin-treated VSMC. Exoenzyme C3, a specific Rho A inhibitor, completely prevents agLDL-induced TF overexpression and partially agLDL-TF activation. Blocking LRP1, the receptor of agLDL, with anti-LRP1 antibodies or inhibiting LRP1 expression by small interference RNA treatment (siRNA-LRP1) impairs agLDL-induced TF overexpression and activation.


CONCLUSIONS
These results demonstrate that TF induction by agLDL depends on LRP1 expression and requires Rho A translocation to the cellular membrane.
Camino-López
S
S
Cardiovascular Research Center, CSIC-ICCC, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.
Llorente-Cortés
V
V
Sendra
J
J
Badimon
L
L
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001692:Biological Transport; D015153:Blotting, Western / Q000379:methods; D001905:Botulinum Toxins / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003331:Coronary Vessels; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D011106:Polyisoprenyl Phosphates / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012717:Sesquiterpenes / Q000494:pharmacology; D019821:Simvastatin / Q000494:pharmacology; D013925:Thromboplastin / Q000032:analysis / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008077:Lipoproteins, LDL; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011106:Polyisoprenyl Phosphates; D012717:Sesquiterpenes; C004808:farnesyl pyrophosphate; D013925:Thromboplastin; D019821:Simvastatin; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein; C002963:geranylgeranyl pyrophosphate