Mutagenesis associated with nitric oxide production in transgenic SJL mice

Abstract

We recently reported development of an experimental model for the study of nitric oxide (NO ⅐ ) toxicology in vivo. SJL mice were injected with superantigen-bearing RcsX (pre-B-cell lymphoma) cells, which migrated to the spleen and lymph nodes, where their rapid growth induced activation of macrophages to produce large amounts of NO ⅐ over a period of several weeks. In the experiments described here, we used this model to investigate mutagenesis in splenocytes exposed to NO ⅐ during RcsX cell growth. Transgenic mice were produced by crossbreeding animals of the pUR288 transgenic C57BL͞6 and SJL strains. RcsX cells were injected into F 1 mice and NO ⅐ production was confirmed by quantification of urinary nitrate, the ultimate metabolite of NO ⅐ . Mutant frequency in the lacZ gene of the pUR288 plasmid was determined in DNA isolated from spleen (target) and kidney (nontarget) tissues. A significant elevation in mutant frequency was found in the spleen, but not in the kidney, of tumor-bearing mice. Furthermore, increases in mutant frequency in the spleen as well as NO ⅐ production were abrogated by administration of N-methylarginine, a NO ⅐ inhibitor, to mice following injection of RcsX cells. These results indicate that NO ⅐ had mutagenic activity in RcsX tumor-bearing mice and thus support a possible role for its involvement in the carcinogenic process.

Neutrophils, Nitric Oxide Synthase, and Mutations in the Mutatect Murine Tumor Model

“…10,18,23,[25][26][27][28][29][30][31] The enzyme responsible for the production of nitric oxide from arginine in tissues is NOS. Immunohistochemical analysis of MN-11 tumors demonstrated iNOS in infiltrating neutrophils and biochemical measurements of tissue extracts showed NOS activity.…”

“…17 In a lacZ transgenic mouse injected with lymphoma cells to produce inflammation in the spleen and lymphatic tissues, an increase in MF in host cells was seen. 18 Thus, the association between chronic inflamma-tion and cancer may be explained by the presence of mutagenic factors in inflammatory milieu.…”

“…24 The nature of the mutagenic species in the tumor microenvironment is unknown, but is suspected of being reactive oxygen species (ROS) or nitrogen species (RNS). 10,18,23,[25][26][27][28][29][30][31] Because ROS and RNS are known to be mutagenic, it is possible that they are responsible for the genotoxicity associated with both the inflammatory and the tumor microenvironments.…”

NO: an inhibitor of cell death

“…Indeed, NOS is often highly expressed in malignant cells. 11,12 NOS not only protects B cells against spontaneous apoptosis but also from apoptosis induced by Fas activation. 9,13 The same apparently holds true for T cells and monocytic cell lines.…”

Nitric oxide and TNF-α trigger colonic inflammation and carcinogenesis in Helicobacter hepaticus -infected, Rag2 -deficient mice

“…Inflammatory bowel diseases (IBDs), such as Crohn's disease and ulcerative colitis, also increase risk for colon cancer (2, 3). Generation of nitric oxide (NO) by inducible NO synthase (iNOS) is a central feature of chronic inflammatory diseases in the gastrointestinal tract (4-9), but precise mechanistic roles for NO in colon cancer development remain undefined.Colon cancer patients exhibit evidence of nitrosative and oxidative stresses that increase cancer risk (10), resulting from mutagenic reactive oxygen and nitrogen species derived from NO generated by immune cells (6,(11)(12)(13)(14)(15). Roles for chronic bacterial infection in IBD and colon cancer have been identified recently in recombinase-activating gene-2-deficient mice (Rag2 Ϫ/Ϫ ), which completely lack functional lymphocytes (16-18).…”