High glucose causes upregulation of cyclooxygenase-2 and alters prostanoid profile in human endothelial cells: role of protein kinase C and reactive oxygen species.
BACKGROUND
Prostaglandins generated by cyclooxygenase (COX) have been implicated in hyperglycemia-induced endothelial dysfunction. However, the role of individual COX isoenzymes as well as the molecular mechanisms linking oxidative stress and endothelial dysfunction in diabetes remains to be clarified.


RESULTS
Human aortic endothelial cells were exposed to normal (5.5 mmol/L) and high (22.2 mmol/L) glucose. Glucose selectively increased mRNA and protein expression of COX-2. Its upregulation was associated with an increase of thromboxane A2 and a reduction of prostacyclin (PGI2) release. Glucose-induced activation of PKC resulted in the formation of peroxynitrite and tyrosine nitration of PGI2 synthase. NO release was reduced despite 2-fold increase of endothelial NO synthase expression. Phorbol ester caused an increase of COX-2 and endothelial NO synthase expression similar to that elicited by glucose. These effects were prevented by the PKC inhibitor calphostin C. N-acetylcysteine, vitamin C, and calphostin C prevented ROS formation, restored NO release, and reduced colocalization of nitrotyrosine and PGI2 synthase. Expression of p22(phox), a subunit of NAD(P)H oxidase, was increased, and diphenyleneiodonium inhibited ROS formation. By contrast, indomethacin did not affect glucose-induced ROS generation.


CONCLUSIONS
Thus, high glucose, via PKC signaling, induces oxidative stress and upregulation of COX-2, resulting in reduced NO availability and altered prostanoid profile.
Cosentino
Francesco
F
Department of Cardiovascular Research, Institute of Physiology, University of Zurich and Cardiovascular Center, University Hospital, Zurich, Switzerland. f_cosentino@hotmail.com
Eto
Masato
M
De Paolis
Paola
P
van der Loo
Bernd
B
Bachschmid
Markus
M
Ullrich
Volker
V
Kouroedov
Alexei
A
Delli Gatti
Chiara
C
Joch
Hana
H
Volpe
Massimo
M
Lüscher
Thomas F
TF
D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism*; D011464:Epoprostenol / Q000378:metabolism; D005786:Gene Expression Regulation; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000378:metabolism; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics; D008565:Membrane Proteins; D008954:Models, Biological; D019255:NADPH Oxidases / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D018384:Oxidative Stress; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D011453:Prostaglandins / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013928:Thromboxane A2 / Q000096:biosynthesis; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis; D015854:Up-Regulation
D007527:Isoenzymes; D008565:Membrane Proteins; D011453:Prostaglandins; D017382:Reactive Oxygen Species; C002744:3-nitrotyrosine; D014443:Tyrosine; D013928:Thromboxane A2; D003577:Cytochrome P-450 Enzyme System; D011464:Epoprostenol; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D019255:NADPH Oxidases; D011493:Protein Kinase C; D019746:Intramolecular Oxidoreductases; C022461:prostacyclin synthetase; D005947:Glucose; D013755:Tetradecanoylphorbol Acetate