Cytokinesis-Block Micronucleus Cytome Assays for the Determination of Genotoxicity and Cytotoxicity of Cecal Water in Rats and Fecal Water in Humans

Abstract

We tested the cytokinesis-block micronucleus cytome assay using the WIL2-NS human B lymphoblastoid cell line as a biomarker of genotoxicity and cytotoxicity of cecal water from rats and fecal water from humans. Cecal water was assessed in rats fed either a diet rich in fat, low in calcium and fiber, and barbecued red meat as the protein source (high colorectal cancer risk diet) or a diet high in fiber and calcium, low in fat, and casein as the protein source (low colorectal cancer risk diet) for 2 weeks. There was a significant 7.6-, 1.8-, and 4.0-fold increase in binucleated (BN) cells with micronuclei (Mn-BN), BN cells with nucleoplasmic bridges (Npb-BN), and necrotic cells (P < 0.001) with 1-h incubation with a 10% dilution of the cecal water isolated from rats fed the high colorectal cancer risk diet compared with rats fed the low colorectal cancer risk diet. In humans, fecal water samples collected from feces of free-living volunteers showed that 24-h exposure to 1% dilution of fecal water produced a significant 2.6-, 6.5-, 7.5-, and 2.2-fold increase in Mn-BN, Npb-BN, BN cells with nuclear buds, and necrotic cells compared with controls (P < 0.05). The coefficients of variations for interindividual differences for Mn-BN, Npb-BN, BN cells with nuclear buds, and necrosis biomarkers were greater than corresponding coefficients of variations for intraindividual variation. These results indicate that the cytokinesis-block micronucleus cytome assay can be used successfully to determine the interindividual variation in genotoxicity and cytotoxicity of cecal or fecal water and to identify dietary patterns that are likely to increase carcinogenic events in the colon. (Cancer Epidemiol Biomarkers Prev 2007;16(12):2676 -80)

In vitrotoxicology studies of extracellular vesicles

“…Cytokinesis‐block micronucleus assay was performed as previously described (Benassi et al, ; Fenach, ; Thomas and Fenech, ). Briefly, CHO‐K1 cells were incubated for 24 h at 37 °C with EVs, 5 or 10 μ m etoposide as a positive control or PBS as a negative control.…”

Impact of the gut microbiota, prebiotics, and probiotics on human health and disease

“…Proteins and peptides reaching the colon are fermented by intestinal bacteria to yield a great diversity of end products, including branched-chain fatty acids, such as isobutyrate and isovalerate, along with ammonia, amines, N-nitroso compounds, phenols, in doles, thiols, CO 2 , H 2 , and sulfur-containing compounds such as H 2 S, many of which have toxic properties [21] that have been associated with colon cancer [22] and inflammatory bowel disease. [23] An increase of the dietary protein load in healthy individuals results in enhanced generation of these toxins, many of which are cleared by the kidneys.…”

Impact of microbial transformation of food on health—from fermented foods to fermentation in the gastro-intestinal tract

“…When proteins and peptides reach the colon they can serve as substrates for fermentation by gut microbiota. Dissimilatory metabolism of proteins in the gut can lead to the production of compounds that can be disadvantageous and even toxic to the host, include ammonia, amines, phenols, thiols, indols, N-nitroso-compounds, branched chain fatty acids and sulfide [65,66] that has been associated with colon cancer [67] and inflammatory bowel diseases [68].…”