The significance of azo-reduction in the mutagenesis and carcinogenesis of azo dyes

Azo dyes are widely used in textile, printing, cosmetic, drug and food-processing industries. They are also used extensively in laboratories as either biological stains or pH indicators. The extent of such use is related to the degree of industrialization. Since intestinal cancer is more common in highly industrialized countries, a possible connection may exist between the increase in the number of cancer cases and the use of azo dyes. Azo dyes can be reduced to aromatic amines by the intestinal microflora. The mutagenicity of a number of azo dyes is reviewed in this paper. They include Trypan Blue, Ponceau 3R, Pinceau 2R, Methyl Red, Methyl Yellow, Methyl Orange, Lithol Red, Orange I, Orange II, 4-Phenylazo-Naphthylamine, Sudan I, Sudan IV, Acid Alizarin Violet N, Fast Garnet GBC, Allura Red, Ponceau SX, Sunset Yellow, Tartrazine, Citrus Red No. 2, Orange B, Yellow AB, Carmoisine, Mercury Orange, Ponceau S, Versatint Blue, Phenylazophenol, Evan's Blue and their degraded aromatic amines. The significance of azo reduction in the mutagenesis and carcinogenesis of azo dyes is discussed.     

Dietary intake of artificial food color additives containing food products by school-going children

Nutritional risk in children is associated with food safety. This is the first study to identify the food type consumed by 6–17-year-old school-going children in Saudi Arabia. Eight permitted artificial food color additives, including Tartrazine (E102), Sunset Yellow (E110), Carmoisine (E122), Allura Red (E129), Indigo Carmine (E132), Brilliant Blue (E133), Fast Green (E143), and Black PN (E151), and two non-permitted ones, Erythrosine (E127) and Red 2G (E128), were determined using 24-h dietary recall questionnaires. Artificial color additives in 839 food products were divided into nine categories, including biscuits, cakes, chocolates, chips, ice cream, juices and drinks, candy, jelly, and chewing gum, are determined using high performance liquid chromatography and diode array detector. The results indicated a high intake of juices and drinks, ice cream, and cakes, but low consumption of chewing gum among school-going children. Among the permitted artificial food color additives, Brilliant Blue (E133) (54.1%) and Tartrazine (E102) (42.3%) were the most commonly used. Sunset Yellow (E110) in one chocolate sample, Tartrazine (E102) and Sunset Yellow (E110) in one and two juice and drink samples, respectively, and Brilliant Blue (E133) in two candy samples exceeded the permitted level. Therefore, further investigations are needed to provide insights into the possible adverse health effects of high intake of these additives in artificial food coloring on the test population are warranted.     

Highly sensitive and accurate screening of 40 dyes in soft drinks by liquid chromatography-electrospray tandem mass spectrometry

A method combining solid phase extraction with high performance liquid chromatography-electrospray ionization tandem mass spectrometry was developed for the highly sensitive and accurate screening of 40 dyes, most of which are banned in foods. Electrospray ionization tandem mass spectrometry was used to identify and quantify a large number of dyes for the first time, and demonstrated greater accuracy and sensitivity than the conventional liquid chromatography-ultraviolet/visible methods. The limits of detection at a signal-to-noise ratio of 3 for the dyes are 0.0001-0.01 mg/L except for Tartrazine, Amaranth, New Red and Ponceau 4R, with detection limits of 0.5, 0.25, 0.125 and 0.125 mg/L, respectively. When this method was applied to screening of dyes in soft drinks, the recoveries ranged from 91.1 to 105%. This method has been successfully applied to screening of illegal dyes in commercial soft drink samples, and it is valuable to ensure the safety of food.     

Purification and partial characterization of two azoreductases from Shigella dysenteriae Type 1

Two azoreductases (I and II) were purified to homogeneity from extracts of Shigella dysenteriae (type 1). Azoreductase I was a dimer of identical subunits of M(r) 28,000, whereas azoreductase II was a monomer of 11,000 M(r). Both were flavoproteins, each containing 1 mol of FMN per mol enzyme. Both NADH and NADPH functioned as electron donors for the azoreductases. Azoreductase I used Ponceau SX, Tartrazine, Amaranth and Orange II as substrates. Azoreductase II utilized all the dyes except Amaranth.     

Detection of in vivo genotoxicity of endogenously formed N-nitroso compounds and suppression by ascorbic acid,teas and fruit juices

The genotoxicity of endogenously formed N-nitrosamines from secondary amines and sodium nitrite (NaNO(2)) was evaluated in multiple organs of mice, using comet assay. Groups of four male mice were orally given dimethylamine, proline, and morpholine simultaneously with NaNO(2). The stomach, colon, liver, kidney, urinary bladder, lung, brain, and bone marrow were sampled 3 and 24 h after these compounds had been ingested. Although secondary amines and the NaNO(2) tested did not yield DNA damage in any of the organs tested, DNA damage was observed mainly in the liver following simultaneous oral ingestion of these compounds. The administration within a 60 min interval also yielded hepatic DNA damage. It is considered that DNA damage induced in mouse organs with the coexistence of amines and nitrite in the acidic stomach is due to endogenously formed nitrosamines. Ascorbic acid reduced the liver DNA damage induced by morpholine and NaNO(2). Reductions in hepatic genotoxicity of endogenously formed N-nitrosomorpholine by tea polyphenols, such as catechins and theaflavins, and fresh apple, grape, and orange juices were more effective than was by ascorbic acid. In contrast with the antimutagenicity of ascorbic acid in the liver, ascorbic acid yielded stomach DNA damage in the presence of NaNO(2) (in the presence and absence of morpholine). Even if ascorbic acid acts as an antimutagen in the liver, nitric oxide (NO) formed from the reduction of NaNO(2) by ascorbic acid damaged stomach DNA.     

The comet assay in eight mouse organs: results with 24 azo compounds

The genotoxicity of 24 azo compounds selected from IARC (International Agency for Research on Cancer) groups 2A, 2B, and 3 were determined by the comet (alkaline single cell gel electrophoresis, SCG) assay in eight mouse organs. We treated groups of four mice once orally at the maximum tolerated dose (MTD) and sampled stomach, colon, liver, kidney, bladder, lung, brain, and bone marrow 3, 8, and 24 h after treatment. For the 17 azo compounds, the assay was positive in at least one organ; (1) 14 and 12 azo compounds induced DNA damage in the colon and liver, respectively, (2) the genotoxic effect of most of them was greatest in the colon, and (3) there were high positive responses in the gastrointestinal organs, but those organs are not targets for carcinogenesis. One possible explanation for this discrepancy is that the assay detects DNA damage induced shortly after administration of a relatively high dose, while carcinogenicity is detected after long treatment with relatively low doses. The metabolic enzymes may become saturated following high doses and the rates and pathways of metabolic activation and detoxification may differ following high single doses vs. low long-term doses. Furthermore, considering that spontaneous colon tumors are very rare in rats and mice, the ability to detect tumorigenic effects in the colon of those animals might be lower than the ability to detect genotoxic events in the comet assay. The in vivo comet assay, which has advantage of reflecting test chemical absorption, distribution, and excretion as well as metabolism, should be effective for estimating the risk posed by azo dyes to humans in spite of the difference in dosage regimen.     

Semicontinuous decolorization of azo dyes by rotating disc contactor immobilized with<Emphasis Type="Italic">Aspergillus sojae</Emphasis> B-10

Aspergillus sojae B-10 was immobilized and used to treat model dye compounds. The model wastewater, containing 10 ppm of azo dyes such as Amaranth, Sudan III, and Congo Red, was treated with cells attached to a rotating disc contactor (RDC). Amaranth was decolorized more easily than were Sudan III and Congo Red. Decolorization of Amaranth began within a day, and the dye was completely decolorized within 5 days of incubation. Both Sudan III and Congo Red were almost completely decolorized after 5 days of incubation. Semicontinuous decolorization of azo by reusing attached mycelia resulted in almost complete decolorization in 20 days. This experiment indicated that decolorization was successfully conducted by removing azo dyes withAspergillus sojae B-10.     

Resveratrol, melatonin, vitamin E, and PBN protect against renal oxidative DNA damage induced by the kidney carcinogen KBrO3.

Free radical scavengers can protect against the genotoxicity induced by chemical carcinogens by decreasing oxidative damage. The protective effect of the antioxidants melatonin, resveratrol, vitamin E, butylated hydroxytoluene and 2-mercaptoethylamine, and the spin-trapping compound alpha-phenyl-N-tert-butyl nitrone (PBN) against oxidative DNA damage was studied in the kidney of rats treated with the kidney-specific carcinogen potassium bromate (KBrO3). KBrO3 was given to rats previously treated with melatonin, resveratrol, PBN, vitamin E, butylated hydroxytoluene, or 2-mercaptoethylamine. Oxidative damage to kidney DNA was estimated 6 hours afterwards by measuring 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxo8dG) referred to deoxyguanosine (dG) by means of high performance liquid chromatography with electrochemical-coulometric and ultraviolet detection. Levels of oxo8dG in the renal genomic DNA significantly increased by more than 100% after the KBrO3 treatment. This increase was completely abolished by the treatment with resveratrol and was partially prevented by melatonin, PBN and vitamin E. Resveratrol and PBN also prevented the increase in relative kidney weight induced by KBrO3. These results show that various different antioxidants and a free radical trap, working in either the water-soluble or the lipid-soluble compartments, can prevent the oxidative DNA damage induced in the kidney by the carcinogen KBrO3.     

Alkaline elution of DNA from stomach pyloric mucosa of rats treated with glyoxal

DNA damage in the pyloric mucosa of the stomach of male F344 rats was determined by the alkaline elution method after administration of glyoxal, a direct-acting mutagen present in various heated foods, by gastric intubation. Glyoxal at doses of 50-550 mg/kg body weight induced DNA damage in the pyloric mucosa of rat stomach, detected by a 5- to 12-fold increase in the elution rate constant 2 h after its administration. N-Methyl-N'-nitro-N-nitrosoguanidine, a glandular stomach carcinogen, used as a positive control at doses of 1-100 mg/kg body weight induced a 11- to 24-fold increase in the elution rate constant, while 2-acetylaminofluorene, which is not a gastric carcinogen, given as a negative control at doses of 200-400 mg/kg body weight did not increase the elution rate constant. Thus glyoxal, which was previously suggested to induce unscheduled DNA synthesis in the pyloric mucosa of rat stomach, was confirmed to be genotoxic in this region.     

Ascorbic Acid Inhibits Lipid Peroxidation but Enhances DNA Damage in Rat Liver Nuclei Incubated with Iron Ions

In this report we studied DNA damage and lipid peroxidation in rat liver nuclei incubated with iron ions for up to 2 hrs in order to examine whether nuclear DNA damage was dependent on membrane lipid peroxidation. Lipid peroxidation was measured as thio-barbituric acid-reactive substances (TBARS) and DNA damage was measured as 8-OH-deoxyguanosine (8-OH-dG). We showed that Fe(II) induced nuclear lipid peroxidation dose-dependently but only the highest concentration (1.0 mM) used induced appreciable 8-OH-dG. Fe(II1) up to 1 mM induced minimal lipid peroxidation and negligible amounts of 8-OH-dG. Ascorbic acid enhanced Fe(II)-induced lipid peroxidation at a ratio to Fe(II) of 1:l but strongly inhibited peroxidation at ratios of 2.5:l and 5:l. By contrast, ascorbate markedly enhanced DNA damage at all ratios tested and in a concentration-dependent manner. The nuclear DNA damage induced by 1 niM FeSO₄/5 mM ascorbic acid was largely inhibited by iron chelators and by dimethylsulphoxide and manni-tol, indicating the involvement of OH. Hydrogen peroxide and superoxide anions were also involved, as DNA damage was partially inhibited by catalase and, to a lesser extent, by superoxide dismutase. The chain-breaking antioxidants butylated hydroxytoluene and diphenylamine (an alkoxyl radical scavenger) did not inhibit DNA damage. Hence, this study demonstrated that ascorbic acid enhanced Fe(II)-induced DNA base modification which was not dependent on lipid peroxidation in rat liver nuclei.     

Sweet taste receptor agonists alter ovarian functions and ovarian cycles in aged mice

Saccharine sodium and rebaudioside A are low-calorie sweeteners, and the biologic effects of these sweeteners in rat ovaries are related to the activity of sweet taste receptors. Data on the impact and regulatory mechanisms underlying such sweeteners on the reproduction of aged animals are currently lacking. In the present study we assessed how the consumption of sweeteners affects the ovarian cycle, ovulation, biochemical indices, and other biologic functions. Thirty-six 1-year-old mice were randomly divided into 3 groups: a control (C) group receiving regular water, a saccharin sodium group receiving a 7.5 mM solution, and the rebaudioside A group receiving a 2.5 mM solution for 30 days. We observed no significant changes in body weights in any group. However, uterine weight in the rebaudioside A group significantly increased in diestrus, and we recorded a significant increase in the percentage of abnormal estrous cycles and the number of corpora lutea in the treatment groups. TUNEL staining and Immunoreactivity for the apoptosis-inducing factor (AIF) confirmed apoptosis in granulosa cells, oocyte, and corpus luteum. Serum glucose increased significantly in both treatment groups and there was a significant increase in cholesterol in the rebaudioside A group. Furthermore, the saccharin sodium-treated group exhibited elevated serum progesterone levels compared with the other groups. In conclusion, sweeteners manifested deleterious effects on reproductive indices in aged mice.     

In vivo short-term assays for tumor initiation and promotion in the glandular stomach of Fischer rats

Here we summarize the data on 55 compounds tested in in vivo short-term assays for tumor-initiating and tumor-promoting activity in the glandular stomach of male Fischer (F344) rats. Most of the data has been previously published. Tumor-initiating activity was assayed by measuring the induction of unscheduled DNA synthesis (UDS) and DNA single strand scission; tumor-promoting activity was assayed by measuring the induction of ornithine decarboxylase (ODC) activity, increased replicative DNA synthesis (RDS), and of c-fos and c-myc oncogene expression. The compounds were orally administered. Twenty-nine compounds were tested for UDS. Eight were positive, including 5 glandular stomach carcinogens; 16 were negative, including 5 liver carcinogens; and 5 were equivocal. Twenty compounds were tested for DNA single strand scission. Twelve were positive, including 6 glandular stomach carcinogens; 7 negative, including 2 liver carcinogens; and 1 was equivocal. Thirty-two compounds were tested for RDS. Twenty-six were positive, including 8 glandular stomach carcinogens and 6 glandular stomach tumor-promoters; 4 were negative, including 3 liver carcinogens and a stomach irritant; and 2 were equivocal. Forty-five compounds were tested for ODC. Thirty-seven were positive, including 8 glandular stomach carcinogens and 6 glandular stomach tumor promoters; 7 were negative, including 3 liver carcinogens; and one was equivocal. All glandular stomach carcinogens and tumor-promoters examined were positive in both RDS and ODC. Two compounds were tested for c-fos and c-myc expression; one was a glandular stomach carcinogen and one was a glandular stomach tumor promoter, and both were positive. In addition, 2 compounds inhibited the increase in RDS induced by the tumor promoter NaCl, suggesting anti-tumor-promoter activity. Thus these assays are useful for assessing potential tumor-initiating and tumor-promoting activity in the rat glandular stomach.     

Evaluation of a new model to detect bladder carcinogens or co-carcinogens; results obtained with saccharin, cyclamate and cyclophosphamide.

A sensitive rat model has been designed to detect potential weak bladder carcinogens or co-carcinogens. The test compound is given to animals which have received a single initiating, but non-carcinogenic, dose of N-methyl-N-nitrosourea (MNU). The model has been used to investigate two compounds currently under suspicion as weak bladder carcinogens, namely sodium saccharin and sodium cyclamate, and one compound known to be cytotoxic but not carcinogenic for the bladder epithelium namely cyclophosphamide. For comparison, these three compounds were also tested as solitary carcinogens in animals not pre-treated with MNU. At the very high dose levels used, sodium saccharin and sodium cyclamate were weak solitary carcinogens producing 4/253 and 3/228 bladder tumours respectively, and the first of these tumours did not appear for more than 80 weeks. When tested in the MNU/rat model more than half the animals receiving either sodium saccharin or sodium cyclamate developed bladder tumours from 10 weeks onwards. By contrast, cyclophosphamide failed to produce any tumours when tested either as a solitary carcinogen or in the MNU/rat model. It must be emphasized that the doses of saccharin and cyclamate used were far higher than those consumed by man, including diabetics, and these results should not be directly extrapolated to man without careful consideration of many other factors including negative epidemiological findings. The theoretical basis of the model is discussed and also the relevance, in terms of environmental human exposure, of detecting compounds which have a synergistic effect with other known bladder carcinogens. It appears that this model can be used to detect a carcinogenic or co-carcinogenic potential in compounds which are organotropic for the bladder more rapidly and with fewer animals than if the compounds are tested as solitary carcinogens by more conventional methods. It is suggested that it could be used to detect those compounds which require further investigation.     

The modifying effect of sodium ascorbate on DNA damage and repair after N-methyl-N′-nitro-N-nitrosoguanidine treatment in vivo

A biological reducing agent, sodium ascorbate, was used to modify both the damage induced by N-methyl-N′-nitro-N-nitrosoguanidine to mouse gastric mucosal cell DNA and the repair of that damage $\text{in vivo}$. Freshly-mixed carcinogen and sodium ascorbate enhanced DNA fragmentation as measured by shifts in alkaline sucrose gradient sedimentation profiles whereas incubation of the two compounds for a short period resulted in reduced DNA fragmentation. Furthermore, periodic administration of sodium ascorbate following stomach cell DNA damage with carcinogen inhibited DNA repair.     

Acute cell death in various sections of the gastrointestinal tract in DNA synthesis inhibition]

Injection of hydroxyurea induced degeneration of almost all the cells synthesizing DNA in the crypts of the jejunum and of only 10% of such cells in the epithelium of the glandular stomach in mouse. Inhibition of the DNA synthesis by hydroxyurea was complete in both tissues. Thus, the cells of the glandular stomach withstood inhibition of the DNA synthesis without and degeneration.     

In vivo bioassay to detect irinotecan-stabilized DNA/topoisomerase I complexes in rats

Irinotecan is an anticancer agent that stabilizes topoisomerase I/DNA complexes. So far, no test system has been reported for directly determining irinotecan-induced stabilization of topoisomerase I/DNA complexes in organs in vivo. We adapted an ‘in vivo complexes of enzyme to DNA’ (ICE) bioassay to assess irinotecan activity in the stomach, duodenum, colon and liver of male Wistar rats after a single treatment with irinotecan (100 mg/kg body weight, intraperitoneally). This was compared to the control group receiving 0.9% sodium chloride intraperitoneally. In addition, the DNA strand breaking properties of irinotecan were measured in mucosal cells from the distal colon by single-cell gel electrophoresis (comet assay) to investigate the association of topoisomerase poisoning and DNA damage in vivo. A single dose of irinotecan significantly increased amounts of topoisomerase I covalently bound to DNA in stomach, duodenum, colon and liver. Concomitantly, the irinotecan-treated group showed significantly higher amounts of DNA strand breaks in colon mucosa cells compared to the control group. The ICE bioassay and the comet assay represent two test systems for investigating the impact of topoisomerase I poisons on DNA integrity in colon tissues of Wistar rats.     

Inhibition of Clostridium botulinum by antioxidants, phenols, and related compounds.

A total of 75 compounds, including antioxidants, preservatives, gallic acid and p-hydroxybenzoic acid esters, hydroquinones, hydroxyquinolines, phenol derivatives, and related compounds, were screened for their antibotulinal activity in prereduced Thiotone-yeast extract-glucose broth. The most effective inhibitors of Clostridium botulinum growth and toxin production were long-chain esters of p-hydroxybenzoic acid and gallic acid, antioxidants, and butylphenol derivatives. The antioxidant nordihydroguaiaretic acid at 100 microgram/ml delayed the growth and toxin production for the entire incubation period (7 days). Other antioxidants, such as butylated hydroxytoluene, butylated hydroxyanisole, and tert-butylhydroquinone were also very effective (at 200 to 400 microgram/ml) for the inhibition of C. botulinum growth and toxin production. Toxin was detected, although no detectable growth was found by daily absorbance measurements, in the prereduced medium containing 50 to 400 microgram of 8-hydroxyquinoline, pentylphenol, tert-pentylphenol, 3,5-ditert-butylphenol, 3,5-ditert-butylcatechol, (2-hydroxydiphenyl)methane, or (4-hydroxydiphenyl)methane per ml.     

In vivo genotoxicity of ortho-phenylphenol, biphenyl, and thiabendazole detected in multiple mouse organs by the alkaline single cell gel electrophoresis assay

In Japan, ortho-phenylphenol (OPP), biphenyl (BP), and thiabendazole (2-(4'-thiazolyl)benzimidazole, TBZ) are commonly used as a postharvest treatment to preserve imported citrus fruits during transport and storage. We used a modification of the alkaline single cell gel electrophoresis (SCG) (Comet) assay to test the in vivo genotoxicity of those agents in mouse stomach, liver, kidney, bladder, lung, brain, and bone marrow. CD-1 male mice were sacrificed 3, 8, and 24 h after oral administration of the test compounds. OPP (2000 mg/kg) induced DNA damage in the stomach, liver, kidney, bladder, and lung, BP (2000 mg/kg) and TBZ (200 mg/kg) induced DNA damage in all the organs studied. For OPP, increased DNA damage peaked at 3–8 h and tended to decrease at 24 h. For BP, on the contrary, increased DNA migration peaked at 24 h. That delay may have been due to the fact that OPP is metabolized by cytochrome 450 and prostaglandin H synthase to phenylbenzoquinone (PBQ), a DNA binding metabolite, and BP is metabolized to PBQ via OPP and m-phenylphenol. The positive response to TBZ, an aneugen, supports the in vivo DNA-damaging action of TBZ.     

Lipid peroxidation-related 1,N2-propanodeoxyguanosine-DNA adducts induced by endogenously formed 4-hydroxy-2-nonenal in organs of female rats fed diets supplemented with sunflower, rapeseed, olive or coconut oil

Animal and epidemiological studies confirm an impact of the fatty-acid composition in the diet on cancer development. We investigated the role of supplementation of the diet of female F344-rats with sunflower, rapeseed, olive or coconut oil on the formation of the promutagenic, exocyclic 1,N2-propanodeoxyguanosine adduct of the main lipid peroxidation product 4-hydroxy-2-nonenal in the mucosa of the glandular stomach, the small intestine, the colon, the whole kidney and the lung. This adduct is considered as the predominant DNA adduct arising from lipid peroxidation. The correlations between adduct levels and the different fatty acids were not uniform for all organs. No clear relationships between fatty acids and adduct levels were found in the colon. Significant positive correlations were observed between linoleic acid, total polyunsaturated fatty acids (PUFAs), vitamin E and DNA adduct levels in the small intestine and in the kidney. The results indicate an increasing effect on cancer risk in these organs as a result of high intake of linoleic acid. Inverse relationships between linoleic acid, PUFA and vitamin E intake and adduct levels were found in the glandular stomach and the lung. We could not confirm a chemopreventive effect of linolenic acid (C-18 omega-3 PUFA) on the formation of adducts in our animal study, as was shown in white blood cells of women in a previous study. A tendency towards a decrease in adduct levels was seen with monounsaturated fatty acids (MUFAs) in all organs except the lung. Saturated fatty acids showed a significant positive correlation with adduct levels in the mucosa of the glandular stomach and a significant inverse correlation in the small intestine. Saturated fatty acids are not considered to directly influence lipid peroxidation to a major extent.     

Dextran sulfate sodium-induced ulcerative colitis leads to increased hematopoiesis and induces both local as well as systemic genotoxicity in mice

Ulcerative colitis is a chronic gastrointestinal disorder eliciting the risk of colorectal cancer, the third most common malignancy in humans. The present study was aimed to characterize dextran sulfate sodium-induced ulcerative colitis and to elucidate its influence on the bone marrow cell proliferation and the subsequent stimulation of the systemic genotoxicity in mice. Experimental colitis was induced in Swiss mice using 3% (w/v) dextran sulfate sodium in drinking water. The severity of colitis was assessed on the basis of clinical signs, colon length, oxidative stress parameters, various pro-inflammatory markers, histopathological evaluation and immunohistochemical staining of 8-oxo-7,8-dihydro-2'-deoxyguanosine in the colon of dextran sulfate sodium treated mice. Further, assessment of genotoxicity was carried out using alkaline and modified comet assays in the colon and lymphocytes and micronucleus assay in the peripheral blood of mice. For the evaluation of inflammation-induced cell proliferation in the bone marrow, proliferating cell nuclear antigen immunostaining was carried out in the bone marrow of mice. Dextran sulfate sodium induced severe colitis as evident from the elevated disease activity index, reduced colon length, increased oxidative stress, histological abnormalities and oxidative DNA damage in the colon of mice. Moreover, colitis-induced elevated prostaglandin-E2 level in the plasma of dextran sulfate sodium treated mice stimulated the cell proliferation in the bone marrow, which further triggered colitis-induced DNA damage in the peripheral blood of mice.