Initial Response of Endothelial Cells to Acute Stimulation with a Lipid Component: Increase Cyclooxygenase Activity by Induction of COX-2 through Activation of Tyrosine Kinase†
Duangporn Plasen PhD*, Pravit Akarasereenont MD, PhD*, Kitirat Techatraisak MD, PhD**, Sirikul Chotewuttakorn MSc*, Athiwat Thaworn BSc*
Affiliation : †Present address: Department of Pharmacology, Faculty of Medicine, Srinakarinwirot University, Bangkok, Thailand
* Department of Pharmacology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand
** Department of Obstetric and Gynecology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok,
Thailand
Objective : To study the initial response of endothelial cells acutely stimulated with a lipid component in the
aspect of cyclooxygenase (COX) function which needed for prostacyclin synthesis, an endogenous antiathero-
genic agent secreted from endothelial cells.
Material and Method: 25 hydroxycholesterol (25OHC) was used as a representative lipid component for
stimulating human umbilical vein endothelial cell (HUVEC) obtained from umbilical cords of healthy newborns
with informed consent of their mothers. HUVEC were treated with 25OHC (0.1, 1 or 10 microgram/mL) at times
6, or 24 h. COX activity was measured from amount of 6-keto-PGF1alfa production in the presence of exogenous
arachidonic acids (10 micromolar; 10 min) by enzyme immunoassay. The amount of COX-1 and COX-2 protein
were detected by Western blot. Cell viability was assessed by using MTT assay.
Results : 25OHC induced COX-2 protein production with increasing the activity of COX enzyme in HUVEC
without change in amount of COX-1 protein. The induction of COX-2 or increasing in COX activity depended
on concentration of 25OHC and time to exposure which seemed to be inhibited by genistein, a specific tyrosine
kinase inhibitor.
Conclusion : Acute stimulation of HUVEC with 25OHC, an atherosclerotic lipid component, increases the
activity of COX by inducing COX-2 expression in a manner that depended on concentration and time. The
induction of COX-2 expression might possibly mediated through activation protein tyrosine kinase. These
responses may be an initial defensive mechanism of endothelial cells from lipid component attack.
Keywords : Cyclooxygenase 2, COX-2, Lipids, Oxidized LDL, 25-hydroxycholesterol, Human umbilical vein endothelial cell, HUVEC, Atherosclerosis, Tyrosine kinase
