Mechanisms of inhibitory activity of the aldose reductase inhibitor, epalrestat, on high glucose-mediated endothelial injury: neutrophil-endothelial cell adhesion and surface expression of endothelial adhesion molecules.
BACKGROUND
We have previously reported that endothelial cells cultured in the presence of high concentrations of glucose (27.8 and 55.5 mM) exhibited enhanced neutrophil adhesion through increased expression of endothelial adhesion molecules via the activation of a protein kinase C (PKC)-dependent pathway. We also found that the aldose reductase inhibitor, epalrestat, inhibited these events, but the mechanisms for this inhibition remained unclear. In this study, we further investigated the inhibitory mechanisms of epalrestat with reference to PKC activation and nitric oxide (NO) production.


METHODS
Human umbilical vein endothelial cells (HUVECs) were cultured for 48 h in glucose-rich medium and neutrophils from healthy volunteers were then added and allowed to adhere for 30 min. Adhered neutrophils were quantified by measuring myeloperoxidase (MPO) activity and surface expression of endothelial adhesion molecules was determined by enzyme immunoassay.


RESULTS
Culture in the presence of a high concentration of glucose (27.8 mM for 48 h) increased neutrophil-endothelial cell adhesion and surface expression of intercellular adhesion molecule-1 (ICAM-1), P-selectin, and E-selectin on endothelial cells. These phenomena were significantly inhibited by epalrestat (10 microM), while NO synthase (NOS) inhibitors reduced the inhibitory effects of this compound. In contrast, 10 nM phorbol 12-myristate 13-acetate (PMA), a PKC activator, showed similar effects as high glucose, and these effects were also inhibited by epalrestat.


CONCLUSIONS
Our data suggested that epalrestat inhibited high glucose-mediated neutrophil-endothelial cell adhesion and expression of endothelial adhesion molecules not only through inhibition of a PKC-dependent pathway, but also through increased endothelial NO production.
First Department of Internal Medicine, Nagoya City University Medical School, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan. nokaya@med.nagoya-cu.ac.jp
Naotsuka
N
Okayama
Hitoshi
H
Omi
Masahiro
M
Okouchi
Kenro
K
Imaeda
Takashi
T
Kato
Masaya
M
Akao
Seiji
S
Imai
Manabu
M
Shimizu
Tatsuya
T
Fukutomi
Makoto
M
Itoh
D000449:Aldehyde Reductase / Q000037:antagonists & inhibitors*; D002448:Cell Adhesion / Q000187:drug effects*; D015815:Cell Adhesion Molecules / Q000235:genetics*; D002478:Cells, Cultured; D019040:E-Selectin / Q000235:genetics; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D007700:Kinetics; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D019007:P-Selectin / Q000235:genetics; D009195:Peroxidase / Q000378:metabolism; D012236:Rhodanine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D053778:Thiazolidines; D014471:Umbilical Veins
D015815:Cell Adhesion Molecules; D019040:E-Selectin; D004791:Enzyme Inhibitors; D019007:P-Selectin; D053778:Thiazolidines; D018799:Intercellular Adhesion Molecule-1; C038131:epalrestat; D012236:Rhodanine; D000449:Aldehyde Reductase; D009195:Peroxidase; D013755:Tetradecanoylphorbol Acetate