The natural protective mechanism against hyperglycemia in vascular endothelial cells: roles of the lipid peroxidation product 4-hydroxydodecadienal and peroxisome proliferator-activated receptor delta.
OBJECTIVE
Vascular endothelial cells (VECs) downregulate their rate of glucose uptake in response to hyperglycemia by decreasing the expression of their typical glucose transporter GLUT-1. Hitherto, we discovered critical roles for the protein calreticulin and the arachidonic acid-metabolizing enzyme 12-lipoxygenase in this autoregulatory process. The hypothesis that 4-hydroxydodeca-(2E,6Z)-dienal (4-HDDE), the peroxidation product of 12-lipoxygenase, mediates this downregulatory mechanism by activating peroxisome proliferator-activated receptor (PPAR) delta was investigated.


METHODS
Effects of 4-HDDE and PPARdelta on the glucose transport system and calreticulin expression in primary bovine aortic endothelial cells were evaluated by pharmacological and molecular interventions.


RESULTS
Using GW501516 (PPARdelta agonist) and GSK0660 (PPARdelta antagonist), we discovered that high-glucose-induced downregulation of the glucose transport system in VECs is mediated by PPARdelta. A PPAR-sensitive luciferase reporter assay in VECs revealed that high glucose markedly increased luciferase activity, while GSK0660 abolished it. High-performance liquid chromatography analysis showed that high-glucose incubation substantially elevated the generation of 4-HDDE in VECs. Treatment of VECs, exposed to normal glucose, with 4-HDDE mimicked high glucose and downregulated the glucose transport system and increased calreticulin expression. Like high glucose, 4-HDDE significantly activated PPARdelta in cells overexpressing human PPAR (hPPAR)delta but not hPPARalpha, -gamma1, or -gamma2. Moreover, silencing of PPARdelta prevented high-glucose-dependent alterations in GLUT-1 and calreticulin expression. Finally, specific binding of PPARdelta to a PPAR response element in the promoter region of the calreticulin gene was identified by utilizing a specific chromatin immunoprecipitation assay.


CONCLUSIONS
Collectively, our data show that 4-HDDE plays a central role in the downregulation of glucose uptake in VECs by activating PPARdelta.
Riahi
Yael
Y
Department of Pharmacology, School of Pharmacy, Faculty of Medicine, The Hebrew University, Jerusalem, Israel.
Sin-Malia
Yoav
Y
Cohen
Guy
G
Alpert
Evgenia
E
Gruzman
Arie
A
Eckel
Juergen
J
Staels
Bart
B
Guichardant
Michel
M
Sasson
Shlomo
S
D000447:Aldehydes / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D037282:Calreticulin / Q000235:genetics; D002417:Cattle; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D005947:Glucose / Q000494:pharmacology; D051272:Glucose Transporter Type 1 / Q000235:genetics; D006801:Humans; D006943:Hyperglycemia / Q000517:prevention & control*; D015227:Lipid Peroxidation / Q000502:physiology*; D047494:PPAR delta / Q000187:drug effects / Q000502:physiology*; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics; D011817:Rabbits; D013844:Thiazoles / Q000494:pharmacology
C480745:4-hydroxydodeca-2,6-dienal; D000447:Aldehydes; D037282:Calreticulin; C425931:GW 501516; D051272:Glucose Transporter Type 1; D047494:PPAR delta; D012333:RNA, Messenger; D013844:Thiazoles; D012313:RNA; D005947:Glucose