Induction of cyclin A gene expression by homocysteine in vascular smooth muscle cells.
Homocysteine is an important and independent risk factor for arteriosclerosis. We showed previously that homocysteine stimulates vascular smooth muscle cell proliferation, a hallmark of arteriosclerosis. We show here that homocysteine and serum increased DNA synthesis synergistically in both human and rat aortic smooth muscle cells (RASMCs). Treatment of quiescent RASMCs with 1 mM homocysteine or 2% calf serum for 36 h increased cyclin A mRNA levels by 8- and 14-fold, respectively, whereas homocysteine plus serum increased cyclin A mRNA levels by 40-fold, indicating a synergistic induction of cyclin A mRNA. Homocysteine did not increase the half-life of cyclin A mRNA (2.9 h), but it did increase the transcriptional rate of the cyclin A gene in nuclear run-on experiments. The positive effect of homocysteine on cyclin A gene transcription was confirmed by our finding that homocysteine increased cyclin A promoter activity and ATF-binding protein levels in RASMCs. Finally, 1 mM homocysteine increased cyclin A protein levels and cyclin A-associated kinase activity by threefold. This homocysteine-induced expression lesions by promoting proliferation of vascular smooth muscle cells.
Tsai
J C
JC
Cardiovascular Biology Laboratory, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
Wang
H
H
Perrella
M A
MA
Yoshizumi
M
M
Sibinga
N E
NE
Tan
L C
LC
Haber
E
E
Chang
T H
TH
Schlegel
R
R
Lee
M E
ME
D051696:Activating Transcription Factors; D000818:Animals; D001161:Arteriosclerosis / Q000209:etiology; D001483:Base Sequence; D000077214:Becaplermin; D001769:Blood; D001798:Blood Proteins / Q000032:analysis; D002417:Cattle; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000032:analysis; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004357:Drug Synergism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006710:Homocysteine / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D006656:Protamine Kinase / Q000378:metabolism; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000032:analysis; D014158:Transcription, Genetic / Q000187:drug effects*
D051696:Activating Transcription Factors; D001798:Blood Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D016213:Cyclins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D014157:Transcription Factors; D006710:Homocysteine; D000077214:Becaplermin; D004247:DNA; D006656:Protamine Kinase