1-(1-glycero)dodeca-1-3-5-7-9-pentaene and 1-(1-glycero)tetradeca-1-3-5-7-9-pentaene

Colorectal cancer is one of the most common internal malignancies in Western society. The cause of this disease appears to be multifactorial and involves genetic as well as environmental aspects. The human colon is continuously exposed to a complex mixture of compounds, which is either of direct dietary origin or the result of digestive, microbial and excretory processes. In order to establish the mutagenic burden of the colorectal mucosa, analysis of specific compounds in feces is usually preferred. Alternatively, the mutagenic potency of fecal extracts has been determined, but the interpretation of these more integrative measurements is hampered by methodological shortcomings. In this review, we focus on exposure of the large bowel to five different classes of fecal mutagens that have previously been related to colorectal cancer risk. These include heterocyclic aromatic amines (HCA) and polycyclic aromatic hydrocarbons (PAH), two exogenous factors that are predominantly ingested as pyrolysis products present in food and (partially) excreted in the feces. Additionally, we discuss N-nitroso-compounds, fecapentaenes and bile acids, all fecal constituents (mainly) of endogenous origin. The mutagenic and carcinogenic potency of the above mentioned compounds as well as their presence in feces, proposed mode of action and potential role in the initiation and promotion of human colorectal cancer are discussed. The combined results from in vitro and in vivo research unequivocally demonstrate that these classes of compounds comprise potent mutagens that induce many different forms of genetic damage and that particularly bile acids and fecapentaenes may also affect the carcinogenic process by epigenetic mechanisms. Large inter-individual differences in levels of exposures have been reported, including those in a range where considerable genetic damage can be expected based on evidence from animal studies. Particularly, however, exposure profiles of PAH and N-nitroso compounds (NOC) have to be more accurately established to come to a risk evaluation. Moreover, lack of human studies and inconsistency between epidemiological data make it impossible to describe colorectal cancer risk as a result of specific exposures in quantitative terms, or even to indicate the relative importance of the mutagens discussed. Particularly, the polymorphisms of genes involved in the metabolism of heterocyclic amines are important determinants of carcinogenic risk. However, the present

Topics: Amines; Bile Acids and Salts; Colorectal Neoplasms; Cooking; Feces; Heterocyclic Compounds; Humans; Mutagenesis; Mutagens; Nitroso Compounds; Polycyclic Aromatic Hydrocarbons; Polyenes; Risk Factors

Topics: Animals; Carcinogens; Chemical Phenomena; Chemistry; Humans; Mutagenicity Tests; Polyenes

Topics: Cell Division; Colon; Colonic Neoplasms; Diet; Feces; Humans; Lipids; Polyenes

The response of Escherichia coli to genotoxic agents involves the triggering of a complex system of genes known as the SOS response. In E. coli PQ37, a test organism used for the assessment of genotoxicity, lacZ, the beta-galactosidase gene is placed under the control of sfiA, one of the SOS genes through an operon fusion. The induction of beta-galactosidase activity, when the organism is exposed to genotoxic agents, is an indirect measure of the genotoxic activity of the test compound. Incubation of E. coli PQ37 with either 4-nitroquinoline oxide (4-NQO) or one of the fecal mutagens, fecapentaene-12 or -14 (F-12 or F-14) in the presence of sodium taurocholate or sodium deoxycholate resulted in a significant enhancement of induction of beta-galactosidase activity. The molecular mechanisms of 4-NQO-induced mutagenesis in E. coli are similar to those of the effects of UV light in which both replication-dependent and repair-dependent pathways of mutagenesis exist. Since E. coli PQ37 is excision-repair-deficient, alternate pathways are involved in this system. Bile salts by themselves do not trigger the SOS response, and hence their role in enhancing the SOS-inducing potency of mutagens may involve the potentiation of the cleavage-inactivation of lexA (repressor of SOS) by the protein product of the SOS-controlled gene, recA. The potentiating effect of bile salts on the fecal mutagens, F-12 and F-14, has implications in their suspected role in colon carcinogenesis associated with high-fat, low-fiber diets.

Topics: 4-Nitroquinoline-1-oxide; Alkaline Phosphatase; Bile Acids and Salts; Colonic Neoplasms; Deoxycholic Acid; Dose-Response Relationship, Drug; Drug Synergism; Escherichia coli; Lithocholic Acid; Mutagens; Polyenes; SOS Response, Genetics; Taurocholic Acid; Ultraviolet Rays

Fecapentaenes are a group of fecal mutagens of microbial origin isolated from human stools. Fecapentaene-12 (F-12) and fecapentaene-14 (F-14), differing only in two carbon atoms in the side chain, are glyceryl ethers with a highly reactive chromophoric aliphatic side chain incorporating a conjugated pentaene moiety. Although these compounds are known for their genotoxicity, no test systems have been developed to precisely assess their relative genotoxicity. In this study F-12 and F-14 were assayed for their genotoxicity using the SOS Chromotest in which the induction of beta-galactosidase in E. coli PQ37 was used as a quantitative measure of biological activity. The activity obtained with F-12 and F-14 was compared with that of 4-nitroquinoline oxide (4-NQO) as the reference standard of a direct acting mutagen. While F-14 was almost as active as 4-NQO, F-12 was only about 25% as active as F-14, the higher analog.

Topics: 4-Nitroquinoline-1-oxide; beta-Galactosidase; Enzyme Induction; Escherichia coli; Humans; Mutagenicity Tests; Mutagens; Polyenes; SOS Response, Genetics; Spectrophotometry, Ultraviolet

To determine nonscorbutic effects of moderate vitamin C deficiency we measured immune function and oxidative damage in eight healthy men (25-43 y) who consumed 5-250 mg/d of ascorbic acid over 92 d on a metabolic unit. During ascorbic acid intakes of 5, 10, or 20 mg/d, subjects attained a state of moderate ascorbic acid deficiency as ascorbic acid concentrations in plasma, leucocytes, semen, and buccal cells dropped to less than 50% of baseline with no scorbutic symptoms observed. No changes in cell proliferation, erythrocyte antioxidant enzymes, and DNA strand breaks were observed; however, blood levels of glutathione and NAD(P) decreased during ascorbic acid deficiency, as did delayed hypersensitivity responsiveness. Concentrations of the oxidatively modified DNA base, 8-hydroxydeoxyguanosine in sperm DNA and fecapentaenes, ubiquitous fecal mutagens, were increased during ascorbic acid depletion. Moderate vitamin C deficiency, in the absence of scurvy, results in alteration of antioxidant chemistries and may permit increased oxidative damage.

Topics: Adult; Ascorbic Acid; Ascorbic Acid Deficiency; Humans; Immunocompetence; Male; Oxidants; Polyenes

Fecapentaenes, highly potent fecal mutagens originating from intestinal bacterial production, have been suggested to play an essential role in the initiation of colorectal cancer. Reviewing the data on fecapentaene occurrence in man, the applied methodologies for fecapentaene extraction and analysis appear to be very inconsistent. Therefore, we compared several methods and developed an optimal extraction and purification procedure for fecapentaene quantification in human feces. This method is based upon a dichloromethane extraction of freeze-dried material with application of a Potter homogenization instrument and subsequent HPLC analysis in combination with photodiode array detection. This system enables us to detect and quantify at least eight forms of fecapentaene-like substances generally occurring in human stool. We suggest that these peaks represent fecapentaene-12 (FP-12) and fecapentaene-14, both with a geometric isomer, as well as fecapentaene analogues that have never been reported before. Applying this methodology on feces of a group of young healthy persons, we were able to detect fecapentaene levels ranging from less than 5 micrograms to 6 mg/kg feces, and in 40% of the samples greater than 1.0 mg/kg feces. The newly identified fecapentaenes represent 21.7% of total fecapentaene concentration. It appears that some fecapentaenes are excreted in higher amounts by females as compared to males. Furthermore, we found that fecal mutagenicity to Salmonella tester strain TA100 appeared lower than hypothesized on the basis of overall fecapentaene contents, and that fecal extracts diminish the mutagenic effect of synthetic FP-12 dramatically. Apparently, optimal conditions for fecapentaene extraction result also in an increased level of co-extracted anti-mutagenic substances. Determination of fecal mutagenicity as an index for fecapentaene excretion or colorectal cancer risk is therefore not suitable. In order to assess the relevance of fecapentaenes in the etiology of colorectal cancer, we suggest that a distinction should be made between relative occurrence and degree of genotoxic effect in situ of the various fecapentaene analogues.

Topics: Adult; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Drug Stability; Feces; Female; Genetic Variation; Humans; Male; Mutagenicity Tests; Mutagens; Polyenes; Salmonella

Fecapentaene-12 and -14, direct-acting mutagens in human feces, were found to hydroxylate the C-8 position of guanine residues in DNA in vitro. Fecapentaene-12 or -14 was incubated with 0.5 mg of calf thymus DNA in 1 ml of reaction mixture at pH 7.4 for 2 h at 37 degrees C in the dark, and then 8-hydroxydeoxyguanosine (8-OH-dG) was analyzed. In these conditions 8-OH-dG was formed dose-dependently at levels of 1.1-4.6 residues/10(4) dG with concentrations of 0.5-3.0 mM of fecapentaene-12. Similar results were obtained with fecapentaene-14. The amount of 8-OH-dG in untreated DNA was 0.2-0.3 residue/10(4) dG.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Chemical Phenomena; Chemistry; Deoxyguanosine; DNA; DNA Damage; Free Radicals; In Vitro Techniques; Polyenes

The direct mutagenic activities of a pair of naturally-occurring and several synthetic fecapentaenes were measured in the Ames/Salmonella test system. We found that strain TA100 with preincubation was the most sensitive procedure for the naturally-occurring fecapentaene-12 (FP-12). Its natural analog, FP-14, and the synthetic isomer, cis-FP-12, yielded similar mutagenic activities to FP-12 in the range of 1000-2000 TA100 revertants per microgram of compound. The synthetic analogs of FP-12 and FP-14, MFP-12 and MFP-14, wherein the glycerol moiety was replaced by methoxy, exhibited consistently higher mutagenic activities than their parent fecapentaenes (MFP-12 was about 20 times more potent than FP-12; MFP-14 was about twice the potency of FP-14). The standard rat liver metabolizing system (S9) reduced the activities of all the fecapentaenes in a dose-related manner.

Topics: Animals; Dose-Response Relationship, Drug; Male; Microsomes, Liver; Mutagenicity Tests; Mutagens; Polyenes; Rats; Rats, Inbred Strains; Salmonella typhimurium

Topics: Bile Acids and Salts; Carcinogens; Cholesterol; Colonic Neoplasms; Diet; Dietary Fats; Feces; Humans; Ketosteroids; Mutagenicity Tests; Mutagens; Polyenes; Structure-Activity Relationship

Topics: Adult; Bacteroides; Carcinogens; Colonic Neoplasms; Feces; Female; Humans; Male; Middle Aged; Mutagens; Polyenes

Fecapentaene-14 and -12 are directly acting mutagens that do not require metabolic activation. Their unusual structure suggests a possible mechanism of action. A carbocation that is formed by the addition of an electrophilic species (such as a proton) to the enol ether is most probably the reactive species. A series of model enol ethers with conjugated systems of various lengths was prepared, and a correlation between mutagenicity and increasing reactivity of derived carbocations was found. The glycerol moiety does not play a crucial role in the overall reactivity of the fecapentaenes.

Topics: Alkylating Agents; Mutagenicity Tests; Mutagens; Mutation; Polyenes; Salmonella typhimurium; Structure-Activity Relationship

It has been shown by an HPLC analysis using a quarternary solvent mixture in an isocratic mode that human excretors of these fecal mutagens excrete both fecapentaene -12 and -14 but the ratios vary greatly between individuals. Since these mutagens are produced by the bacterial flora of the colon, this may indicate differences in the flora between these individuals or differences in the availability of different precursor molecules in their colons. Any relationship of these findings to the etiology of colonic cancer is not clear.

Topics: Adult; Bacteria; Chromatography, High Pressure Liquid; Colon; Feces; Female; Humans; Male; Mutagens; Polyenes

Topics: Chemical Phenomena; Chemistry; Chromatography, Gas; Feces; Humans; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Conformation; Mutagens; Polyenes