Lysophosphatidic acid induction of tissue factor expression in aortic smooth muscle cells.
OBJECTIVE
Tissue factor (TF), the initiator of the coagulation cascade, is expressed by cells in atherosclerotic lesions. Lysophosphatidic acid (LPA) is a component of oxidized lipoproteins and an agent released by activated platelets. The present study investigated whether and how TF expression is regulated by LPA.


RESULTS
Northern blotting, Western blotting, and TF activity assays demonstrated that LPA markedly induced TF mRNA, protein, and activity in vascular smooth muscle cells. LPA-induced TF expression is primarily controlled at the transcriptional level. Phosphorylation of mitogen-activated protein kinase kinase (MEK) and extracellular signaling-regulated kinases (ERK1/2) was rapidly and markedly induced by LPA. MEK inhibitors U0126 and PD98059 blocked both ERK activation and the increase in TF mRNA. In contrast, the specific p38 MAP kinase inhibitor SB203580 had no effect on LPA-induced TF mRNA increase. The Galpha(i) protein inhibitor, pertussis toxin, abolished LPA-induced phosphorylation of MEKs and ERKs, as well as the induction of TF mRNA.


CONCLUSIONS
Our data demonstrate that a Galpha(i) protein and activation of MEKs and ERKs mediate LPA-induced TF expression. Our data suggest that elevated LPA could be a thrombogenic risk factor by upregulating TF expression. These results may have important implications in vascular remodeling and vascular diseases.
Cui
Mei-Zhen
MZ
Department of Pathology, University of Tennessee, Knoxville 37996, USA. cuim@utk.edu
Zhao
Guojun
G
Winokur
Allison L
AL
Laag
Essam
E
Bydash
Jason R
JR
Penn
Marc S
MS
Chisolm
Guy M
GM
Xu
Xuemin
X
D000818:Animals; D001011:Aorta / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D020962:Heterotrimeric GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D006801:Humans; D008246:Lysophospholipids / Q000378:metabolism / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D020871:RNA Stability / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D051381:Rats; D013925:Thromboplastin / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; D008246:Lysophospholipids; D012333:RNA, Messenger; D013925:Thromboplastin; D037342:Pertussis Toxin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020962:Heterotrimeric GTP-Binding Proteins