Induction of mitotic gene conversion by browning reaction products and its modulation by naturally occurring agents

Lactoferrin could alleviate liver injury caused by Maillard reaction products with furan ring through regulating necroptosis pathway

As classical MRPs, the toxic effects of furosine, pyralline, and 5-hydroxymethylfurfural (5-HMF) in liver tissue are evaluated and the related mechanism is investigated here, and the protective effects of lactoferrin on liver injury caused by Maillard reaction products (MRPs) with furan ring are proved in vitro and in vivo. First, we detect the concentrations of furosine, pyralline, and 5-HMF in several foods using ultrahigh-performance liquid chromatography (UHPLC). Then, the effects of the three MRPs on liver cells (HL-7702) viability, as well as liver tissue, are performed and evaluated. Furthermore, the regulations of three MRPs on necroptosis-related pathway in liver cells are investigated. Additionally, the effects of lactoferrin in alleviating liver injury, as well as regulating necroptosis pathway, were evaluated. Results elucidate that lactoferrin protects liver injury caused by MRPs with furan ring structure through activating RIPK1/RIPK3/p-MLKL necroptosis pathway and downstream inflammatory reaction.

Genotoxicity and mutagenicity of melanoidins isolated from a roasted glucose–glycine model in human lymphocyte cultures, intestinal Caco-2 cells and in the Salmonella typhimurium strains TA98 and TA102 applying the AMES test

Melanoidins are formed during household cooking procedures and are part of our daily diet, but data on their toxicological potential are still scarce. Therefore, the mutagenic, cytotoxic and genotoxic activity of the water soluble total fraction (sol A), the water soluble high molecular weight fraction (HMW; Molecular weight>12,400 Da) and the remaining water soluble low molecular weight fraction (LMW) isolated from a glucose-glycine model system roasted at 125 degrees C was comprehensively studied in human lymphocytes (genetic end point: sister chromatid exchange (SCE)), Caco-2 cells (SCE, cell viability, cell proliferation) and in the Salmonella typhimurium strains TA98 and TA102 (Ames test). Tests were performed in a dose- and time-dependent manner. The results indicate a significant increase in SCE formation in human lymphocytes after the exposure to 0.05% and 0.1% of the melanoidin fractions. In Caco-2 cells, only the exposure to LMW increased the SCE formation as a matter of concentration. Cell's proliferation and viability decreased significantly after exposure to melanoidins. In the AMES test, melanoidins did not show a mutagenic potential, neither using the TA98 nor the TA102 strain. These results show that melanoidins isolated from the glucose-glycine mixture exhibited modest but significant genotoxic effects in human lymphocytes and, in particular the LMW, in Caco-2 cells, but they induce neither in low nor in very high concentrations mutagenicity in bacteria strains.

Influence of thermally processed carbohydrate/amino acid mixtures on the fermentation by Saccharomyces cerevisiae

The production of alcoholic beverages such as Tequila, Mezcal, whiskey, or beer includes the fermentation of a mash containing Maillard reaction products. Because excessive heating of the mash can lead to complications during the following fermentation step, the impact of Maillard products on the metabolism of Saccharomyces cerevisiae was investigated. For this purpose, fermentation was carried out in a model system in the presence and absence of Maillard reaction products and formation of ethanol served as a marker for the progression of fermentation. We found that increasing amounts of Maillard products reduced the formation of ethanol up to 80%. This effect was dependent on the pH value during the Maillard reaction, reaction time, as well as the carbohydrate and amino acid component used for the generation of Maillard reaction products. Another important factor is the pH value during fermentation: The inhibitory effect of Maillard products was not detectable at a pH of 4 and increased with higher pH-values. These findings might be of relevance for the production of above-mentioned beverages.

Tumor-promoting effect of GGN-MRP extract from the Maillard reaction products of glucose and glycine in the presence of sodium nitrite in C3H10T1/2 cells

GGN-MRP is an extract from the Maillard reaction products of nitrite with glucose and glycine in the Maillard browning system. No genotoxicity of GGN-MRP in culture hepatocyte was found. A two-stage transformation protocol was used to transform chemically mouse embryo fibroblast C3H10T1/2 cells. To initiate transformation, the cells were treated with benzo[a]pyrene [B(a)P; 0.1 microg/mL], and GGN-MRP (0.01, 0.1, and 1.0 mg/mL) was employed to subsequently complete the transformation process. Malignant transformed foci were formed in B(a)P-initiated and GGN-MRP-promoted C3H10T1/2 cells after 8 weeks. Cells treated with GGN-MRP alone failed to induce transformation. However, cells initiated with B(a)P and promoted by GGN-MRP demonstrated oncogenic properties. Transformed colonies derived from GGN-MRP-treated cells exhibited enhanced growth rate, anchorage independence, and tumorgenicity in animals relative to parent cells. These results indicated that GGN-MRP contains a tumor promoter and may induce tumor promotion by two-stage oncogenesis.

Mutagenicity of heated sugar-casein systems: effect of the Maillard reaction

The formation of mutagens after the heating of sugar-casein model systems at 120 degrees C was examined by the Ames test, using Salmonella typhimurium strain TA100. Several sugars (glucose, fructose, galactose, tagatose, lactose, and lactulose) were compared in their mutagenicities. Mutagenicity could be fully ascribed to Maillard reaction products and strongly varied with the kind of sugar. The differences in mutagenicity among the sugar-casein systems were caused by a difference in reaction rate and a difference in reaction mechanism. Sugars with a comparable reaction mechanism (glucose and galactose) showed a higher mutagenic activity corresponding with a higher Maillard reactivity. Disaccharides showed no mutagenic activity (lactose) or a lower mutagenic activity (lactulose) than their corresponding monosaccharides. Ketose sugars (fructose and tagatose) showed a remarkably higher mutagenicity compared with their aldose isomers (glucose and galactose), which was due to a difference in reaction mechanism.

DNA strand-breaking activity and mutagenicity of 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP), a Maillard reaction product of glucose and glycine

Aqueous solution of glucose and glycine was heated under reflux for 4 h and extracted with ethyl acetate. Reversed phase HPLC of the extract revealed a new DNA strand-breaking substance, which was purified by repeated HPLC and identified as 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP). DDMP induced DNA strand breaking in a dose- and time-dependent manner. It was active to break DNA strands at pH 7.4 and 9.4. Its pyranone skeleton was destroyed at the pH values. DNA strand breaking by DDMP was inhibited by superoxide dismutase, catalase, scavengers for hydroxyl radical, spin trapping agents and metal chelators, and the breaking was enhanced by Fe(III) ion. A mixture of DDMP and a spin trap DMPO gave electron spin resonance signals of a spin adduct DMPO-OH, indicating generation of hydroxyl radical. DDMP was found to be mutagenic to Salmonella typhimurium TA100 without metabolic activation. These results show DDMP generated active oxygen species to cause DNA strand breaking and mutagenesis.

DNA strand breaks induced through active oxygen radicals by fragrant component 4-hydroxy-2-hydroxymethyl-5-methyl-3(2H)-furanone in Maillard reaction of hexose/amino acid

The Maillard reaction of glucose/amino acid produces components that induce strand breakage of supercoiled DNA. This study was designed to elucidate the structure of the active components and the mechanisms of their DNA strand breakage. When an aqueous mixture of glucose/glycine heated under reflux for 4 hr was extracted with ethyl acetate, the extract showed mutagenicity to Salmonella typhimurium TA100 and strand-breaking activity for supercoiled DNA. One of the components with DNA strand-breaking activity was isolated by repeated HPLC using a reverse phase column. The component was identified as 4-hydroxy-2-hydroxymethyl-5-methyl-3(2H)-furanone (HHMF), a fragrant component in the Maillard reaction mixture. HHMF was similarly produced in the reaction of glucose/alanine and fructose/glycine. DNA strand-breaking activity of the component at pH 7.4 increased with increasing dose of the component and with increasing incubation time. The strand-breaking activity of the component was greater at pH 7.4 than at pH 4.4 and 9.4; it was inhibited in the presence of superoxide dismutase, catalase, hydroxyl radical scavengers, spin-trapping agents, thiol compounds and metal chelators, and also by removal of dissolved oxygen from the reaction mixture. The strand-breaking activity was enhanced in the presence of ionic iron. Incubation of HHMF with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) gave electron spin resonance signals characteristics of the DMPO-OH adduct, indicating generation of the hydroxyl radical. HHMF generated superoxide, hydrogen peroxide and then hydroxyl radical with the aid of a trace amount of metal ions, which effectively cleaved the DNA strand.

Genotoxicity hazard assessment of Caramel Colours III and IV

Results from a battery of short-term tests in vitro and in vivo used to assess the genotoxicity of caramel colours are presented and discussed in relation to reports from the literature. No evidence of genotoxicity was found in the Salmonella plate incorporation test using five standard strains or in the Saccharomyces cerevisiae gene conversion assay using strain D4, either with or without S-9 for activation. A weak clastogenic effect for a sample of Caramel Colour III in CHO cells was abolished in the presence of S-9. Two samples of Caramel Colour IV were not clastogenic in CHO cells. Salmonella pre-incubation tests without S-9 also failed to reveal any mutagenic activity for any of the caramel colours tested. The Caramel Colour III sample that showed clastogenic activity in CHO cells in vitro did not induce micronuclei when evaluated in a mouse bone marrow assay. These results are in general agreement with reports in the literature regarding the genotoxicity of caramel colours, and support the conclusion that caramel colours do not pose a genotoxic hazard to humans.

Modifying role of dietary factors on the mutagenicity of aflatoxin B1: in vitro effect of trace elements

Using Salmonella typhimurium strains TA100 and TA98 tests have been carried out to detect the inhibitory activity of various trace elements on mutagenesis induced by aflatoxin B1 (AFB1) in the presence of a rat liver microsomal activation system. Several trace elements have shown significant modulating activity in both the strains, while a few show inhibition only in a particular strain. Among the most effective elements are copper, manganese, zinc and selenium, all of which exhibit an inhibition pattern which is dose-dependent. Copper, in particular, shows exceptional activity, since the molar excess dose of this element required to inhibit AFB1 mutagenicity by 50% has been observed to be very low. The action of trace elements is possibly mediated through interaction with microsomal enzymes, thereby modulating the formation of the reactive metabolite before modification of DNA. These results suggest that certain trace elements notably copper may have potential anticarcinogenic activity against AFB1.

Age-correlated DNA damage in human muscle tissue

This investigation represents the largest study so far published on human DNA damage and aging. The subject of this investigation is damage, determined as DNA alterations which give rise to complete molecular breaks in the course of treatment of purified DNA solutions with single-strand-specific nucleases. The DNA is derived from milligram samples of human muscle of individuals mostly undergoing surgical treatment. Care has been taken to bring the muscle samples, once shut off from blood circulation to liquid nitrogen temperatures within few seconds. The DNA is prepared by a procedure keeping breaks by handling and by DNAase attack as low as possible, however pushing DNA purity, especially with respect to protein as high as possible. Highly purified DNA treated in this way has some sites which are susceptible to single-strand (ss) specific DNAase splitting (ss-events). Three different deoxyribonucleases have been used: Nuclease S1, Nuclease BAL31 and Pea Endo-Nuclease. They give very similar results, i.e. splitting of the DNA so as to yield DNA pieces of given distribution. The lengths of these double-strand (ds) pieces have been determined from their electron microscopical pictures, either by following the image contours with a magnetostrictive stylo of the projected photo on a pad, by following the contours with a mileage ruler, or by integrating the silver grains on the photo. The molecular weight averages of the ds DNA threads between two ss-events for each individual have been determined from 20 to 200 molecules. The 470 individuals contributing their data were from age groups from 1 to 91 years. The molecular weights show a considerable scatter with an average molecular weight of the DNA ds pieces between two ss-events of 43.93 MDa and a standard deviation of 17.99 MDa. Among the single-strand breaks (ssb) that split the DNA into such pieces is a fraction, the number of which increases in a highly significant fashion with the age of the donor. From this derives the fact that the average molecular weight of the DNA strand pieces between two ssb decreases with age. It is remarkable that the standard deviation of the molecular weights of such pieces increases with age significantly, too. On the basis of additional information mainly supplied by the DNA donor himself or by his parents the 470 members of the main group M where grouped according to their life-style, into: (1) abstinent people, essentially non-smokers and refraining from use of licit or illicit drugs, sub-group N.(ABSTRACT TRUNCATED AT 400 WORDS)

The influence of pH on the convertogenic activity of plant phenolics

The genotoxicity of plant phenolics, including pyrogallol, gallic acid, resorcinol and catechin, and a water extract and tannin fraction of betel nut (Areca catechu) was examined at pH levels ranging from 5 to 10. Strain D7 of Saccharomyces cerevisiae was used since the cells can withstand a wide range of pH levels without any loss of viability. At alkaline pH ranges, the examined phenolics and betel nut extracts induced mitotic conversion, whereas they lacked this capacity at acid pH levels. This phenomenon may be due to the rapid autoxidation of phenolics under alkaline conditions, which leads to the generation of H2O2 and free radicals. The results indicate that plant phenolics may pose a genotoxic hazard during chewing of lime-containing betel quid and tobacco which causes the salivary pH to rise above 8.

Dietary carcinogens and anticarcinogens. Oxygen radicals and degenerative diseases

The human diet contains a great variety of natural mutagens and carcinogens, as well as many natural antimutagens and anticarcinogens. Many of these mutagens and carcinogens may act through the generation of oxygen radicals. Oxygen radicals may also play a major role as endogenous initiators of degenerative processes, such as DNA damage and mutation (and promotion), that may be related to cancer, heart disease, and aging. Dietary intake of natural antioxidants could be an important aspect of the body's defense mechanism against these agents. Many antioxidants are being identified as anticarcinogens. Characterizing and optimizing such defense systems may be an important part of a strategy of minimizing cancer and other age-related diseases.