Increased expression of cyclooxygenase-2 protein during rat hepatocarcinogenesis caused by a choline-deficient, L-amino acid-defined diet and chemopreventive efficacy of a specific inhibitor, nimesulide.
Expression of cyclooxygenase (COX)-2 protein during rat hepatocarcinogenesis associated with fatty change, fibrosis, cirrhosis and oxidative DNA damage, caused by a choline-deficient, L-amino acid-defined (CDAA) diet were investigated in F344 male rats, along with the chemopreventive efficacy of the specific COX-2 inhibitor, nimesulide (NIM). Nimesulide, which was administered in the diet at concentrations of 200, 400, 600 and 800 p.p.m. for 12 weeks, decreased the number and size of preneoplastic enzyme-altered liver foci, levels of oxidative DNA damage, and the grade and incidence of fibrosis in a dose-dependent manner. A preliminary long-term study of 65 weeks also revealed that 800 p.p.m. NIM decreased the multiplicity of neoplastic nodules and hepatocellular carcinomas and prevented the development of cirrhosis. Western blot analysis revealed that COX-2 protein was barely expressed in control livers and increased approximately 2.9-fold in the livers of rats fed on a CDAA diet for 12 weeks and approximately 4.5-5.4-fold in tumors, with a diameter larger than 5 mm, at 80 weeks. Immunohistochemically, COX-2 protein was positive in sinusoidal and stromal cells in fibrotic septa, which were identified by immunoelectron microscopy as Kupffer cells, macrophages, either activated Ito cells or fibroblasts, after exposure to the CDAA diet for 12 weeks, whereas it was only occasionally weakly positive in sinusoidal, probably Kupffer, cells in control livers. In neoplastic nodules in rats fed on a CDAA diet for 30 and 80 weeks, sinusoidal cells and cells with relatively large round nuclei and scanty cytoplasm were strongly positive for COX-2 protein, with the neoplastic hepatocytes in the minority of the nodules, but not the cancer cells, being moderately positive. These results clearly indicate that rat hepatocarcinogenesis, along with fatty change, fibrosis and cirrhosis, is associated with increased expression of COX-2 protein, and point to the chemopreventive efficacy of a selective COX-2 inhibitor against, at least, the early stages of hepatocarcinogenesis.
Denda
Ayumi
A
Department of Oncological Pathology, Cancer Center, Nara Medical Univesity, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan. adenda@nmu-gw.cc.naramed-u.ac.jp
Kitayama
Wakashi
W
Murata
Akiko
A
Kishida
Hideki
H
Sasaki
Yasutaka
Y
Kusuoka
Osamu
O
Tsujiuchi
Toshifumi
T
Tsutsumi
Masahiro
M
Nakae
Dai
D
Takagi
Hidetoshi
H
Konishi
Yoichi
Y
D000080242:8-Hydroxy-2'-Deoxyguanosine; D000596:Amino Acids / Q000494:pharmacology*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology; D015153:Blotting, Western; D002478:Cells, Cultured; D002794:Choline / Q000494:pharmacology*; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005355:Fibrosis; D005982:Glutathione Transferase / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D007728:Kupffer Cells / Q000648:ultrastructure; D008099:Liver / Q000378:metabolism; D008113:Liver Neoplasms / Q000201:enzymology*; D008297:Male; D008565:Membrane Proteins; D016253:Microscopy, Immunoelectron; D009929:Organ Size / Q000187:drug effects; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D051381:Rats; D011916:Rats, Inbred F344; D013449:Sulfonamides / Q000494:pharmacology*; D013997:Time Factors
D000596:Amino Acids; D016588:Anticarcinogenic Agents; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D013449:Sulfonamides; D000080242:8-Hydroxy-2'-Deoxyguanosine; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat; D005982:Glutathione Transferase; D003849:Deoxyguanosine; D002794:Choline; C012655:nimesulide