Cyclooxygenase 2 and prostaglandin E2 regulate the attachment of calcium oxalate crystals to renal epithelial cells.
OBJECTIVE
To determine the roles of endogenous cyclooxygenase 2 and prostaglandin E(2) in crystal-cell binding, which is considered to be an important step in the development of intratubular nephrocalcinosis.


METHODS
An expression plasmid for human cyclooxygenase 2 was introduced into Madin-Darby canine kidney cells using the lipofection method. Cyclooxygenase activity was measured using thin-layer chromatography, and the prostaglandin E(2) concentration was determined with an enzyme immunoassay. In addition, crystal attachment was evaluated with a liquid scintillation counter using [(14)C] calcium oxalate monohydrate crystals, and immunohistochemistry and an enzyme immunoassay were used to analyze and quantify the expression of hyaluronan, a crystal-binding molecule.


RESULTS
Cyclooxygenase 2-overexpressing Madin-Darby canine kidney cells produced about 10-fold more prostaglandin E(2) than wild-type Madin-Darby canine kidney cells, and their hyaluronan production was also upregulated. The attachment of calcium oxalate monohydrate crystals to cyclooxygenase 2-overexpressing Madin-Darby canine kidney cells was significantly reduced compared with their attachment to wild-type and mock-transfected Madin-Darby canine kidney cells. Pre-incubation of the cyclooxygenase 2-overexpressing cells, as well as the mock-transfected and wild-type cells with the cyclooxygenase 2 selective inhibitor etodolac, increased the cellular attachment of calcium oxalate monohydrate crystals in a dose-dependent manner.


CONCLUSIONS
These findings suggest that cyclooxygenase 2 expression and the resultant increase in endogenous prostaglandin E(2), leading to increased hyaluronan production, help to prevent nephrocalcinosis by inhibiting the attachment of calcium oxalate monohydrate crystals to the surface of renal epithelial cells.
Department of Urology, Kanazawa Medical University, Uchinada, Ishikawa, Japan. miyazawa@kanazawa-med.ac.jp
Katsuhito
K
Miyazawa
Yoshitaka
Y
Takahashi
Nobuyo
N
Morita
Manabu T
MT
Moriyama
Takeo
T
Kosaka
Matomo
M
Nishio
Tanihiro
T
Yoshimoto
Koji
K
Suzuki
D000268:Adhesiveness / Q000187:drug effects; D000818:Animals; D002129:Calcium Oxalate / Q000378:metabolism*; D002478:Cells, Cultured; D003460:Crystallization; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism*; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism*; D017308:Etodolac / Q000494:pharmacology; D005822:Genetic Vectors; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D009397:Nephrocalcinosis / Q000378:metabolism*; D010957:Plasmids
D052246:Cyclooxygenase 2 Inhibitors; D002129:Calcium Oxalate; D017308:Etodolac; D006820:Hyaluronic Acid; D051546:Cyclooxygenase 2; D015232:Dinoprostone