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Weill Medical College of Cornell University, Departments of Pediatrics and Medicine, New York, NY 10021
2To whom correspondence should be addressed.
Homocysteine (HC) is a highly reactive thiol intermediate in amino acid
metabolism, which can modify the function of endothelial cells in a
myriad of ways. In vitro, homocysteine can inhibit the
thromboresistance properties of the endothelial cell by induction of
procoagulant factors, inactivation of natural anticoagulant systems,
and suppression of vasodilatory and platelet-modulating factors. HC
also inhibits the fibrinolytic system by impairing the ability of the
endothelial cell to bind tissue plasminogen activator (t-PA), by
interacting directly with the t-PA binding "tail" domain of its
endothelial cell receptor, annexin II. Moreover, HC influences
endothelial cell gene expression as exemplified by induction of the
elongation factor-1 family of polypeptides, which promote polypeptide
chain elongation during mRNA translation. Induction of EF-1 subunits
, ß,
and
by homocysteine is associated with increased
turnover of at least one free thiolcontaining protein, suggesting
that up-regulation of these subunits may represent a mechanism for
replacement of damaged or modified proteins. A more complete
understanding of the diverse effects of homocysteine on endothelial
cell function may provide important clues to the precise role
homocysteine may play in the initiation and progression of vascular
disease.
KEY WORDS: homocysteine elongation factors endothelial cell tissue plasminogen activator plasmin