Journal Article

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

Ayumi Denda, Wakashi Kitayama, Akiko Murata, Hideki Kishida, Yasutaka Sasaki, Osamu Kusuoka, Toshifumi Tsujiuchi, Masahiro Tsutsumi, Dai Nakae, Hidetoshi Takagi and Yoichi Konishi

in Carcinogenesis

Volume 23, issue 2, pages 245-256
Published in print February 2002 | ISSN: 0143-3334
Published online February 2002 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/23.2.245
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

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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 ~2.9-fold in the livers of rats fed on a CDAA diet for 12 weeks and ~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.

Keywords: CDAA, choline-deficient, l-amino acid-defined; CDML, choline-deficient, methionine-low; COX, cyclooxygenase; CSAA, choline-supplemented, l-amino acid-defined; DNase, deoxyribonuclease; GST-P, glutathione S-transferase placental form; HCC, hepatocellular carcinoma; HE, hematoxylin and eosin; HGF, hepatocyte growth factor; 8-OHdG, 8-hydroxydeoxyguanosine; LPS, lipopolysaccharide; MEM, minimum essential medium; NIM, nimesulide; NSAID, non-steroidal anti-inflammatory drug; PG, prostaglandin; PBS, phosphate-buffered saline; TBS, Tris-buffered saline; TGF, transforming growth factor

Journal Article.  8956 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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