Expression of thrombomodulin in atherosclerotic lesions and mitogenic activity of recombinant thrombomodulin in vascular smooth muscle cells.
Thrombomodulin (TM), a thrombin receptor protein found on the endothelial cell surface, contains 6 tandem epidermal growth factor (EGF)-like structures. Recombinant human TM peptide containing these 6 EGF-like domains (rTME1-6) exhibits mitogenic activity in Swiss 3T3 cells. We examined the localization of TM in atherosclerotic lesions and the effects of rTME1-6 on the growth of cultured rat vascular smooth muscle cells (SMCs). Immunohistochemical analysis demonstrated that TM antigen was localized on monocytes, macrophages, and vascular SMCs. In cultured vascular SMCs, rTME1-6 accelerated [3H]thymidine uptake into DNA in a dose-dependent manner up to 3.4 times the control level. This mitogenic activity was abolished by addition of polyclonal anti-human TM antibody. The rTME1-6-induced mitogenesis was enhanced by EGF. However, a neutralizing monoclonal antibody against the EGF receptor (monoclonal antibody 225) did not inhibit the mitogenic activity of rTME1-6. Calphostin C, a specific protein kinase C inhibitor, and lavendustin-A, an inhibitor of EGF receptor-specific protein tyrosine kinase, inhibited the mitogenic activities of both rTME1-6 and EGF. Finally, rTME1-6 treatment increased the level of phosphorylated mitogen-activated protein kinase in SMCs. Together, these results suggest that TM expression in atherosclerotic lesions may be associated with promotion of atherosclerosis through its mitogenic activity in vascular SMCs.
Tohda
G
G
Third Department of Internal Medicine, Faculty of Medicine, Fukui Medical University, Fukui, Japan.
Oida
K
K
Okada
Y
Y
Kosaka
S
S
Okada
E
E
Takahashi
S
S
Ishii
H
H
Miyamori
I
I
D000368:Aged; D000818:Animals; D001161:Arteriosclerosis / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D066246:ErbB Receptors / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008934:Mitogens / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D009281:Naphthalenes / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000494:pharmacology; D018180:Thrombomodulin / Q000032:analysis* / Q000502:physiology; D013936:Thymidine / Q000378:metabolism
D008934:Mitogens; D009281:Naphthalenes; D011994:Recombinant Proteins; D018180:Thrombomodulin; D004247:DNA; D066246:ErbB Receptors; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C058819:calphostin C; D013936:Thymidine