Homocysteine inhibits arterial endothelial cell growth through transcriptional downregulation of fibroblast growth factor-2 involving G protein and DNA methylation.
Homocysteine (Hcy) contributes to atherogenesis and angiostasis by altering the phenotype of arterial endothelial cells (ECs). The present study was aimed at elucidating potential mechanisms by which Hcy can slow EC proliferation and induce EC apoptosis, thereby disrupting endothelial integrity. Given the strong mitogenic and antiapoptotic properties of fibroblast growth factor (FGF)2, we examined whether Hcy can modulate its expression. In cultured human coronary and bovine aortic ECs, Hcy exerted time- and concentration-dependent (0 to 500 micromol/L) reduction of the mRNA and protein levels of FGF2, whereas vascular endothelial growth factor expression was not affected until Hcy reached a proapoptotic 500 micromol/L. By testing a panel of signal transduction inhibitors, we found that the Hcy-induced downregulation of FGF2 was specifically attenuated by pertussis toxin, an inhibitor of Gi protein signaling. Hcy induced cell cycle arrest at the G(1)/S transition and increased TUNEL-positive apoptotic cells in a graded manner. These effects were effectively counteracted by exogenous FGF2. Reporter gene assays showed that Hcy downregulated FGF2 by transcriptional repression of the gene promoter encompassed in a CpG dinucleotide-rich island. This region was heavily methylated at the cytosine residues by Hcy despite decreased methylation potential (S-adenosylmethionine to S-adenosylhomocysteine ratio). Normal levels of FGF2 transcription were restored to ECs simultaneously exposed to Hcy and 5-aza-deoxycytidine. We conclude that homocysteine disrupts the growth and survival of ECs through a G protein-mediated pathway associated with altered promoter DNA methylation and the transcriptional repression of FGF2.
Chang
Po-Yuan
PY
Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
Lu
Shao-Chun
SC
Lee
Chii-Ming
CM
Chen
Yi-Jie
YJ
Dugan
Tracey A
TA
Huang
Wen-Huei
WH
Chang
Shwu-Fen
SF
Liao
Warren S L
WS
Chen
Chu-Huang
CH
Lee
Yuan-Teh
YT
D000818:Animals; D001158:Arteries / Q000166:cytology*; D002417:Cattle; D049109:Cell Proliferation / Q000187:drug effects*; D019175:DNA Methylation; D015536:Down-Regulation / Q000187:drug effects; D042783:Endothelial Cells / Q000166:cytology*; D016222:Fibroblast Growth Factor 2 / Q000235:genetics*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006711:Homocystine / Q000494:pharmacology*; D014158:Transcription, Genetic
D016222:Fibroblast Growth Factor 2; D006711:Homocystine; D019204:GTP-Binding Proteins