nitroarginine and Adenocarcinoma

We previously reported the cancer chemopreventive activity of 4'-geranyloxyferulic acid (GOFA, Miyamoto et al., Nutr Cancer 2008; 60:675-84) and a β-cyclodextrin inclusion compound of GOFA (Tanaka et al., Int J Cancer 2010; 126:830-40) in colitis-related colorectal carcinogenesis. In our study, the chemopreventive effects of a newly synthesized GOFA-containing compound, GOFA-N(omega)-nitro-L-arginine methyl ester (L-NAME), which inhibits inducible nitric oxide (iNOS) and cyclooxygenase-2 (COX) enzymes, were investigated using a colitis-associated mouse colorectal carcinogenesis model with azoxymethane (AOM) and dextran sodium sulfate (DSS). The dietary administration of GOFA-L-NAME after the AOM and DSS treatments significantly reduced the multiplicity of adenocarcinomas (inhibition rates: 100 ppm, 84%, p < 0.001; 500 ppm, 94%, p < 0.001) compared with the AOM + DSS group. Dietary GOFA-L-NAME significantly decreased the proliferation (p < 0.001) and increased the apoptosis (p < 0.001) of colonic adenocarcinoma cells. A subsequent short-term experiment revealed that dietary GOFA-L-NAME decreased the mRNA expression of inflammatory enzymes, such as iNOS and COX-2, and proinflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and macrophage inflammatory protein (MIP)-2 in the colonic mucosa of mice that received 1.5% DSS in their drinking water for 7 days. Our findings indicate that GOFA-L-NAME is able to inhibit colitis-associated colon carcinogenesis by modulating inflammation, proliferation, apoptosis and the expression of proinflammatory cytokines in mice.

Topics: Adenocarcinoma; Adenoma; Animals; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Carcinogenesis; Cell Proliferation; Colorectal Neoplasms; Coumaric Acids; Cyclooxygenase 2; Cytokines; Disease Models, Animal; Gene Expression Regulation, Neoplastic; Inflammation; Intestinal Mucosa; Male; Mice; Mice, Inbred ICR; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type II; Nitroarginine; RNA-Binding Proteins

Topics: Aconitate Hydratase; Adenocarcinoma; Amino Acid Oxidoreductases; Animals; Arginine; Cell Line; Interferon-gamma; Iron-Regulatory Proteins; Leukemia P388; Lipopolysaccharides; Macrophages; Mice; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; omega-N-Methylarginine; Recombinant Proteins; RNA-Binding Proteins; RNA, Messenger; Tumor Cells, Cultured; Vasodilator Agents

Antitumour agents such as flavone acetic acid, xanthenone acetic acid (XAA), 5,6-dimethylxanthenone-4-acetic acid and tumour necrosis factor-alpha, following single dose administration to mice with colon 38 adenocarcinomas, induce tumour haemorrhagic necrosis and an elevation in plasma nitrate. The relationship between these two effects has been studied using firstly a series of methyl-substituted XAA derivatives with varying antitumour activity, and secondly the inhibitors NG-monomethyl-L-arginine (NMMA), N-nitro-L-arginine (NNA) and canavanine, which affect nitric oxide synthesis. Elevation of plasma nitrate resulting from the oxidation of L-arginine by nitric oxide synthase is inhibited by NNA rather than by NMMA or canavanine. The results demonstrate that tumour necrosis can be induced in the absence of a significant elevation of plasma nitrate.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Arginine; Canavanine; Colonic Neoplasms; Flavonoids; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Inbred Strains; Necrosis; Nitrates; Nitric Oxide; Nitroarginine; omega-N-Methylarginine; Xanthenes; Xanthones

Nitric oxide (NO) has been previously shown to inhibit crude preparations of ribonucleotide reductase, a key enzyme in DNA synthesis, and to destroy the essential tyrosyl free radical in pure recombinant R2 subunit of the enzyme. In R2-overexpressing TA3 cells, a decrease in the tyrosyl radical was observed by whole-cell EPR spectroscopy, as soon as 4 h after NO synthase induction by immunological stimuli. Complete loss of the tyrosyl EPR signal occurred after 7 h in cells cultured at a high density. Disappearance of the tyrosyl radical was prevented by N omega-nitro-L-arginine, a specific inhibitor of NO synthesis, and by oxyhemoglobin, which reacts rapidly with NO. It was reproduced by S-nitrosoglutathione, a NO-releasing molecule. Stable end products of NO synthase metabolism did not affect the radical. Immunoblot analysis of the R2 subunit indicated that expression of the protein was not influenced by NO synthase activity. These results establish that NO, or a labile product of NO synthase, induces the disappearance of the R2-centered tyrosyl radical. Since the radical is necessary for ribonucleotide reductase activity, its destruction by NO would contribute markedly to the antiproliferative action exerted by macrophage-type NO synthase.

Topics: Adenocarcinoma; Amino Acid Oxidoreductases; Animals; Arginine; Blotting, Western; Citrulline; Electron Spin Resonance Spectroscopy; Enzyme Induction; Free Radicals; Kinetics; Mammary Neoplasms, Experimental; Mice; Nitric Oxide; Nitric Oxide Synthase; Nitrites; Nitroarginine; Ribonucleotide Reductases; Tumor Cells, Cultured; Tyrosine