Studies on the effect of ascorbic acid and selenium on the genotoxicity of nitrofurans: nitrofurazone and furazolidone

Application of furazolidone in Helicobacter pylori infection eradication

Increasing antibiotic resistance is the primary reason for treatment failure of Helicobacter pylori (H. pylori) infection. To enhance the eradication rate, minimize the development of secondary resistance, and alleviate the socioeconomic burden, it is crucial to select H. pylori-sensitive antibiotics carefully. Furazolidone has been used for H. pylori eradication in developing countries for decades due to its affordability and low resistance rate. Numerous studies have demonstrated that furazolidone-containing regimens are more efficacious than those containing other antibiotics, as both first- and second-line therapies, and are also well tolerated. However, utility of furazolidone is restricted or not optimal in certain countries due to its infrequent but potentially severe adverse effects. The decision to discontinue usage of furazolidone because of concerns regarding adverse effects may be misguided. Here we comprehensively reviewed the studies on furazolidone at different dosages and treatment durations for H. pylori eradication. Further research on the mechanisms of action and clinical trials of furazolidone are of great practical importance.

Safety of furazolidone-containing regimen in Helicobacter pylori infection: a systematic review and meta-analysis

OBJECTIVES

Furazolidone containing regimen is effectivefor Helicobacter pylori (H. pylori) infection, but its safetyremains controversial. To assess the safety of furazolidone containing regimenin H. pylori infection.

DESIGN

A systematic review and meta-analysis.

DATA SOURCES

PubMed, Embase, Cochrane Library, Web of Science and Scopus databases were systematically searched for eligible randomised controlled trials.

ELIGIBILITY CRITERIA

Studies comparing furazolidone with non-furazolidone-containing regimen, variable durations or doses of furazolidone were included.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently selected studies and extracted data. Primary outcomes were the risk of total adverse events (AEs), serious AEs and severe AEs, expressed as relative risk (RR) with 95% CI. Secondary outcomes contained the incidence of individual adverse symptoms, AE-related treatment discontinuation and compliance.

RESULTS

Twenty-six articles were identified from 2039 searched records, of which 14 studies (n=2540) compared furazolidone with other antibiotics. The eradication rates of furazolidone-containing regimen were higher than those of other antibiotics in both intention-to-treat (RR 1.06, 95% CI 1.01 to 1.12) and per-protocol analysis (RR 1.05, 95% CI 1.00 to 1.10). Only two serious AEs were reported in furazolidone group (2/1221, 0.16%). No significant increased risk was observed for the incidence of total AEs (RR 1.04, 95% CI 0.89 to 1.21) and severe AEs (RR 1.81, 95% CI 0.91 to 3.60). Twelve studies (n=3139) compared different durations of furazolidone, and four studies (n=343) assessed variable doses. Elevated risk of total AEs and severe AEs were only found in a high daily dose of furazolidone rather than prolonged duration. The incidence of AE-related treatment discontinuation and compliance of patients were all similar, irrespective of dose and duration adjustments.

CONCLUSION

Furazolidone-containing regimen has a similar risk of AEs and compliance as non-furazolidone-containing regimen. A low daily dose of 200 mg is well-tolerated for 14 day regimen and should be first considered.

PROSPERO REGISTRATION NUMBER

CRD42019137247.

Pyoverdine secreted by Pseudomonas aeruginosa as a biological recognition element for the fluorescent detection of furazolidone

Methods for the rapid and sensitive detection of furazolidone, a pesticide used for the treatment of infections of animals and human beings, have been urgently recommended for its large residual, strong carcinogenicity and genotoxicity in the environment. In this study, a method for the detection of furazolidone based on the rapid fluorescence quenching of pyoverdine by furazolidone was developed. Pyoverdine secreted by a Pseudomonas aeruginosa strain PA1 was purified through affinity chromatography and its fluorescent property was characterized. The fluorescence of pyoverdine could be quenched by furazolidone with specificity, and based on this phenomenon a fluorescent method for furazolidone detection was established. Fluorescence of pyoverdine was quenched by furazolidone probably due to the electron transfer from pyoverdine to furazolidone. The optimal pH for the detection was 7.2 in 50 mM 3-(N-Morpholino) propanesulfonic acid solution, and the whole detection process could be completed within a few seconds. The linear range of the detection was 2-160 µM and the limit of detection (LOD) was 0.5 µM. This study developed a novel fluorescent method for furazolidone detection, and the rapid and specific fluorescent biosensor can be potentially applied for furazolidone detection in the aquatic samples.

The influence of organic solvents on estimates of genotoxicity and antigenotoxicity in the SOS chromotest

In this work, the toxicity and genotoxicity of organic solvents (acetone, carbon tetrachloride, dichloromethane, dimethylsulfoxide, ethanol, ether and methanol) were studied using the SOS chromotest. The influence of these solvents on the direct genotoxicity induced by the mutagens mitomycin C (MMC) and 4-nitroquinoline-1-oxide (4-NQO) were also investigated. None of the solvents were genotoxic in Escherichia coli PQ37. However, based on the inhibition of protein synthesis assessed by constitutive alkaline phosphatase activity, some solvents (carbon tetrachloride, dimethylsulfoxide, ethanol and ether) were toxic and incompatible with the SOS chromotest. Solvents that were neither toxic nor genotoxic to E. coli (acetone, dichloromethane and methanol) significantly reduced the genotoxicity of MMC and 4-NQO. When these solvents were used to dissolve vitamin E they increased the antigenotoxic activity of this compound, possibly through additive or synergistic effects. The relevance of these results is discussed in relation to antigenotoxic studies. These data indicate the need for careful selection of an appropriate diluent for the SOS chromotest since some solvents can modulate genotoxicity and antigenotoxicity.

Furazolidone induced oxidative DNA damage via up-regulating ROS that caused cell cycle arrest in human hepatoma G2 cells

Furazolidone (FZD) is an antimicrobial agent that has been shown to have mutagenic, genotoxic and potentially carcinogenic properties when tested in a variety of systems in vitro and in vivo. In this study, we investigated FZD's DNA damaging effect in human hepatoma cells aiming at further defining the molecular mechanism of FZD's cytotoxicity. Addition of FZD resulted in cell growth suppression and cell cycle arrest in S phase accompanied by remarkable DNA strand breaks with increased levels of intracellular reactive oxygen species (ROS) and 8-hydroxydeoxyguanosine. Activities of antioxidases were down-regulated following FZD treatment and antioxidant agent catalase and superoxide dismutase ameliorated FZD's DNA damaging effects. Moreover, FZD caused much more extensive damage to mitochondrial DNA (mtDNA) than to nuclear DNA for which the decrease in mtDNA content correlated with FZD usage in a dose-dependent manner. However, there was no evidence of FZD induced mtDNA mutation in the mitochondrial DNA displacement loop. These results demonstrate that FZD up-regulates the production of intracellular ROS to cause oxidative DNA damage with mtDNA being the most vulnerable targets. Oxidative stress and the injury of mtDNA could be early indicators of FZD-induced cytotoxicity, with the resulting abnormal progression of the cell cycle.

The effect of probiotics on the genotoxicity of furazolidone

Antigenotoxic activity of probiotic bacteria against furazolidone was studied using the short-term bacterial assay SOS chromotest, with Escherichia coli PQ37 as the test organism. The supernatants from probiotic and furazolidone co-incubation exhibited rather strong suppression on SOS induction produced by furazolidone on E. coli PQ 37 (sfiA: lacZ). Genotoxicity inhibition was found for all strains of the examined bacteria belonging to three genera. The highest genotoxicity inhibition was detected for Bifidobacterium lactis Bb-12 (92.0%) and for Lactobacillus acidophilus T20 (81.9%).

Comparative genotoxic evaluation of 2-furylethylenes and 5-nitrofurans by using the comet assay in TK6 cells

The genotoxicity of three 2-furylethylene derivatives and four 5-nitrofurans was evaluated by using the comet assay in human lymphoblastoid cultured TK6 cells. The 2-furylethylene derivatives were 2-furyl-1-nitroethene, 1-(5-bromofur-2-yl)-2-nitroethene and 1-(5-bromofur-2-yl)-2-bromo-2-nitroethene, while the 5-nitrofurans were nitrofurantoin, nitrofurazone, furazolidone and 5-nitro-2-furanacrolein. The treatments lasted for 3 h in the absence of metabolic activation. No genotoxic effects were observed for two of the 2-furylethylene compounds, while the derivative 1-(5-bromofur-2-yl)-2-nitroethene showed a statistically significant response mainly at the highest concentration tested; this effect was considered biologically relevant and the compound was classified as slightly genotoxic. On the other hand, for the classical 5-nitrofurans tested there is a tendency towards a dose-related increase of the DNA damage in the comet assay and the observed increases for the parameters analysed (Olive tail moment, tail % DNA and tail length) were significant for all compounds. Then, the four 5-nitrofurans tested were considered genotoxic. These results show that the position of the nitro group influences the genotoxicity of the assayed compounds. Thus, in this comet assay, the 2-furylethylene derivatives having the nitro group attached outside the furan ring appear to be much less genotoxic than the 5-nitrofurans.

Genotoxicity testing of the furylethylene derivative 1-(5-bromofur-2-yl)-2-bromo-2-nitroethene in cultured human lymphocytes

The genotoxic potential of the compound 1-(5-bromofur-2-yl)-2-bromo-2-nitroethene (G-1) was evaluated in peripheral blood lymphocytes cultured in vitro, at concentrations ranging from 1 to 20 microg/ml. Micronuclei (MN) and sister-chromatid exchanges (SCE) were scored as biomarkers of genotoxic effects. To detect the role of metabolic enzymes on the genotoxicity of this furylethylenic derivative, cultures for MN and SCE demonstrations were treated for 3 h with and without the S9 microsomal fraction as well as for 48 h without S9. Under the conditions of the study, the test agent did not induce significant increases in the frequency of micronucleated cells, irrespective of the presence/absence of the metabolic fraction. Nevertheless, a slight/moderate increase in the SCE frequency was observed in those cultures treated without the S9 mix. In addition, cytotoxic/cytostatic effects of the G-1 compound were observed mainly in cultures without S9 fraction, as indicated by the reduction of cell proliferation measured by the cytokinesis block proliferation index (CBPI) and the proliferative rate index (PRI).

Evaluation of the carcinogenic effects of furazolidone and its metabolites in two fish species

The major metabolite from the use of furazolidone (FZD) in mammals, birds and fish is 2,3-dihydro-3-cyanomethyl-2-hydroxy-5-nitro-1alpha, 2-di(2-oxo-oxazolidin-3-yl)iminomethyl-furo[2,3-beta]furan, also called 3-amine-2-oxazolidone (AOZ). A minor metabolite was identified as N-(5-amine-2-furfuryliden)-3-amine-2-oxazolidone (FOZ). To assess the potential carcinogenicity of FZD and the metabolic mixture of AOZ/FOZ, 11 mg FZD/kg feed/day was fed for 12 weeks to mollies (Poecilia formosa), an ornamental fish species prone to develop tumors. The rate of tumors was quantified and defined both in mollies and their offspring. Then, some fish was made into fishmeal and incorporated into fish food at 500 g of meal/kg of food and fed to other mollies for 12 weeks. The rate of tumors was assessed. A similar trial design was carried out in tilapia fish (Oreochromis niloticus) by adding 50 mg FZD/kg to the feed for 90 days. All animals were placed in glass fishponds under controlled laboratory conditions. Each week, a significant biomass was collected from both groups to assess the macroscopic and histopathological changes. All mollies developed melanohistiocytomic tumors in the liver and other organs. Offspring from surviving mollie females stimulated to breed showed no changes compared to control animals. None of the mollies fed with the mollie-meal food contaminated with AOZ/FOZ developed tumors. Neither tilapia medicated with FZD nor tilapia fed with tilapia-meal contaminated with AOZ/FOZ developed tumors. These results do not support the established viewpoint that FZD must be banned from trophic chains based on its potential carcinogenic properties.

Induction of rat liver cytochrome P450 isoenzymes CYP 1A and CYP 2B by different fungicides, nitrofurans, and quercetin

The genotoxic activity of environmental xenobiotics is manifested either in their direct interaction with cellular genetic material or in provoking secondary events, among which reactive oxygen species (ROS) production is a common phenomenon. Both pathways can be mediated by the activity of the cytochrome P450 monooxygenase system. We studied induction of the CYP 1A or CYP 2B monooxygenases in rat liver by the fungicides: thiram, captan, captafol, dodine and the drugs: nitrofurazone, furazolidone and the plant flavonoid: quercetin. A cytochrome P450 induction assay (CYPIA test) was used. S9 prepared from livers of rats treated with the test compounds were used to activate ethidium bromide (EtBr) (CYP 1A isoenzyme) or cyclophosphamide (CPA) (CYP 2B isoenzyme) in the Ames test. It was found that among the tested compounds, the most potent inducer of CYP 1A was furazolidone (3 x 80 mg/kg). Less potent was thiram (1 x 100mg/kg), as well as quercetin (3 x 80 mg/kg), and captafol (1 x 30 mg/kg). On the other hand, thiram (1 x 100 mg/kg), captafol (1 x 30 mg/kg), and quercetin (3 x 80 mg/kg) were most potent in the CYP 2B isoenzyme induction, while furazolidone (3 x 80 mg/kg), and nitrofurazone (3 x 80 mg/kg) appeared to be less potent in this respect. Captan and dodine (3 x 80 mg/kg) did not affect the activity of any of the cytochrome P450 isoenzymes.

Genotoxic evaluation of the furylethylene derivative 2-furyl-1-nitroethene in cultured human lymphocytes

The compound 2-furyl-1-nitroethene (G-0) was evaluated for genotoxicity in cultured human peripheral blood lymphocytes, at concentrations ranging from 1 to 15microg/ml. Micronuclei (MN) and sister-chromatid exchanges (SCEs) were scored as genetic endpoints. In order to detect the role of metabolic enzymes on the genotoxicity of this furylethylenic derivative, the cultures for MN and SCE demonstrations were also treated with S9 microsomal fraction. The results indicate that, under the conditions of the study, the test agent does not seem to induce significant increases in the frequency of micronucleated cells, irrespective of the presence of metabolic activation. Nevertheless, a slight increase in the SCE frequency was observed in those cultures treated without the S9 mix; although this increase disappeared in presence of the microsomal fraction. In addition, cytostatic effects of 2-furyl-1-nitroethene were observed mainly in cultures without S9 fraction, as indicated by the reduction of cell proliferation.

A mechanistic study of ovarian carcinogenesis induced by nitrofurazone using rasH2 mice

In order to clarify whether the ovarian tumors induced in a long-term carcinogenicity study of nitrofurazone (NF) in mice can be also produced in a short-term model using transgenic (Tg) mice carrying the human c-Ha-ras gene (rasH2 mice), the following 3 experiments were performed. In experiment 1, both rasH2 mice and their wild CB6F1 littermates carrying no c-Ha-ras gene (non-Tg mice) that were fed a diet containing 500 to 1,000 ppm NF for 7 weeks demonstrated ovarian atrophy characterized by decreased labeling indices (LIs) for proliferating cell nuclear antigen (PCNA) in granulosa cells. In experiment 2, increased numbers of atretic follicles and decreased PCNA LIs in granulosa cells were recognized in rasH2 mice given diets containing 250 or 500 ppm NF for 26 weeks, but no tumor induction was grossly observed. In experiment 3, similar ovarian atrophy was observed in association with increased serum luteinizing hormone (LH) levels in both rasH2 and non-Tg mice given diet containing 1,000 ppm NF for 11 days. These results indicate that long-term NF treatment induces ovarian tumors in mice, possibly by continuous stimulation with gonadotropins such as LH via a negative-feedback phenomenon secondary to ovarian atrophy (as the tumor-induction mechanism), although we could not completely rule out a genotoxic mechanism.

Pharmacological, therapeutic and toxicological properties of furazolidone: some recent research

Some of the recent publications on the pharmacological, therapeutic and toxicological properties of the antimicrobial agent furazolidone (FZ) are briefly reviewed. In animals, most of the recently published papers focus on (1) the methodology of measuring the residues of the drug and its metabolites in edible tissues; (2) the carcinogenicity and genotoxicity of FZ; (3) the cellular and molecular basis of FZ-induced cardiomyopthy, and the action of different cardioprotectant drugs thereon; and (4) hormonal effects. In humans, the use of FZ as an anti-ulcer drug and in controlling infectious diseases, especially opportunistic infections in AIDS patients, is described.

Effect of furazolidone on sister-chromatid exchanges, cell proliferation kinetics, and mitotic index in vivo and in vitro

Furazolidone is an antimicrobial compound used in human and veterinary medicine. The aim of this investigation was to determine its genotoxic capacity in vitro and in vivo. We used the human lymphocyte culture system to detect the effect of 2.0, 4.0, 6.0, 8.0, or 10.0 micrograms/ml, and the mouse bone marrow assay to determine the effect of 8.6, 30.0, or 75.0 mg/kg furazolidone. In both systems we determined the frequency of sister-chromatid exchanges (SCE), the cell proliferation kinetics (CPK), and the mitotic index (MI). The in vitro results showed a significant SCE increase starting from the second dose tested and a CPK and MI decrease starting from the third dose. The in vivo results showed a SCE increase with the two high doses tested, but no significant modification was found in the CPK and MI with the three doses tested in the experiment.

Vitamins as antimutagens: advantages and some possible mechanisms of antimutagenic action

Dietary natural inhibitors of mutagenesis and carcinogenesis are of particular importance because they may be useful for human cancer prevention and do not have undesirable xenobiotic effects on living organisms. As was shown in numerous experiments, many endogenous substances, usually obtained in food or synthesized by cells, possess some inhibitory activity towards natural or man-made environmental mutagens which often induce increased frequency of cancer. Among such substances are vitamins, thiol compounds, porphyrin derivatives, polyphenols and others, the antigenotoxicity of which is well established in various genetic tests. Probably a number of these compounds are included in the defense systems of organisms protecting them from harmful exogenous influences continuously affecting genetic material and other components of cells. Some vitamins show protective effects; for example, E, A and C vitamins are active against well-known mutagens both in vitro and in vivo. Genetic properties of other vitamins have been insufficiently explored, but positive results were obtained for a number of them suggesting the desirability of further studies in this field. Synergism of some vitamins activity, both with other vitamins and non-vitamin substances, is of particular interest because clarifying some of their mechanisms of action could be important for understanding the functions of our defense systems.

SOS chromotest results in a broader context: empirical relationships between genotoxic potency, mutagenic potency, and carcinogenic potency

Environmental monitoring requires that large numbers of samples be processed in a relatively short period of time. While microbioassays facilitate rapid testing, the results are often difficult to interpret in the broader context of human or animal health. Determining the consequences of exposure to genotoxic substances will ultimately require in situ monitoring of exposed organisms. However, it is immediately possible to construct a broad empirical framework within which available microbioassay results can be interpreted. To do this for SOS Chromotest results, we investigated the empirical relationships between SOS genotoxic potency and mutagenic potency (as measured with the Salmonella/microsome assay), as well as between genotoxic potency and carcinogenic potency (as measured using standard, chronic animal bioassays). Strong relationships were identified between; 1) genotoxic potency and mutagenic potency for 268 direct-acting substances (r2=0.76) and 2) genotoxic potency and mutagenic potency for 126 S9-activated substances (r2=0.65). Ordinary least squares regression analyses of the SOS genotoxicity-Salmonella mutagenicity relationship revealed a significant effect of SOS genotoxicity as well as differences in mutagenic potency that can be attributed to the Salmonella strain used to measure mutagenic potency. Analyses of S9-activated substances revealed a significant interaction between the SOS genotoxic potency (SOSIP) effect and the Salmonella strain effect. Two regression models relating SOS genotoxicity and Salmonella mutagenicity were used to predict the mutagenic potency of several industrial effluent extracts previously analyzed for SOS genotoxicity by White et al. [(1996): Environ Mol Mutagen 27:116-139]. Predictions are consistent with published mutagenic potency values for similar industrial waste materials. A consistent relationship was also identified between genotoxic potency and carcinogenic potency for 51 substances. Linear regression analyses revealed an effect of SOS genotoxic potency as well as differences in carcinogenic potency that may be attributable to experimental animal and route of exposure. The correlation between genotoxicity and carcinogenicity was fairly weak (maximum r value = 0.51). Previous studies revealed similar strength of association between Ames mutagenicity and carcinogenicity. Predicted carcinogenic potencies of previously examined genotoxic, industrial effluent extracts are generally low compared to the pure substances included in the data set.

Antimutagenicity in Euglena gracilis

The genotoxic effect of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and furadantine (Fu) was significantly decreased by standard antimutagens (ascorbic acid, alpha-tocopherol, chlorophyllin and sodium selenite) in the unicellular flagellate Euglena gracilis. The effects of these compounds were verified also by a bacterial test in which three strains of Salmonella typhimurium, TA97, TA100, and TA102, were used. The above compounds were antimutagenic in strains of bacteria used, except for chlorophyllin which had no effect on strain TA102.

The SOS chromotest: a review

The SOS chromotest is reviewed through over 100 publications corresponding to the testing of 751 chemicals. 404 (54%) of these chemicals present a genotoxic activity detectable in the SOS chromotest. Their SOS inducing potencies span more than 8 orders of magnitude. For 452 compounds, the results obtained in the SOS chromotest could be compared to those obtained in the Ames test. It was found that 373 (82%) of these compounds give similar responses in both tests (236 positive and 137 negative responses). Thus the discrepancies between both tests concern 79 compounds (18%). A case by case analysis shows that many of these compounds are at the same time very weak SOS inducers and very weak mutagens. Thus we think that, most of the time, the discrepancies between the two tests may be accounted for by differences in the interpretation of the results rather than by the experimental results themselves. However, there are some compounds which are clearly SOS inducers but devoid of mutagenic activity in the Ames test (such as quinoline-1-oxide) and to a larger extent, clearly mutagenic compounds which do not induce the SOS response in the SOS chromotest (such as benzidine, cyclophosphamide, acridines, ethidium bromide). We also analyzed the correlation between SOS induction, mutagenesis and carcinogenesis according to the classification of Lewis. For 65 confirmed carcinogens (class 1), the sensitivity, i.e., the capacity to identify carcinogens, was 62% with the SOS chromotest and 77% with the Ames test. For 44 suspected carcinogens (class 2), the sensitivity was 66% with the SOS chromotest and 68% with the Ames test. Thus, we confirmed previous observations made on 83 compounds that there is a close correlation between the results given by both bacterial tests. The capacity of the Ames test to identify carcinogens is higher than that of the SOS chromotest. However, because the number of false positive compounds was lower in the SOS chromotest, the specificity, i.e., the capacity to discriminate between carcinogens and non-carcinogens of the SOS chromotest, appeared higher than that of the Ames test. Thus, the results of the SOS chromotest and of the Ames test can complement each other. The SOS chromotest is one of the most rapid and simple short-term test for genotoxins and is easily adaptable to various conditions, so that it could be used as an early--perhaps the earliest--test in a battery.

Modulation of the H2O2-induced SOS response in Escherichia coli PQ300 by amino acids, metal chelators, antioxidants, and scavengers of reactive oxygen species

The SOS chromotest is a simple colorimetric genotoxicity assay that monitors DNA repair by measuring the induction of the gene sfiA in Escherichia coli K-12. E. coli PQ300, a diagnostic SOS tester strain for the detection of oxidative genotoxins, carries a mutation in a key gene for antioxidative defense, oxyR. This mutation renders PQ300 more sensitive to oxidative genotoxins, particularly to H2O2. We found that induction of the SOS response by H2O2 in E. coli PQ300 is dependent on the composition of the incubation medium; a substantially reduced response was obtained in minimal phosphate buffered saline (PBS) as opposed to complex Luria broth (LB) medium. Supplementation of PBS with histidine or cysteine stimulated H2O2-induced SOS induction to levels exceeding those found in LB medium. Low concentrations of glutathione (20-70 microM) also enhanced the H2O2-induced SOS response in E. coli PQ300, whereas higher concentrations (> 150 microM) were protective. Preincubation of tester cells with the chelators o-phenanthroline, 2,2-dipyridyl, and ethylenediaminetetraacetic acid (EDTA) protected cells from the effects of H2O2, although EDTA was only partially effective. Pretreatment of PQ300 with the antioxidant ascorbic acid or the hydroxyl radical scavenger dimethyl sulfoxide also diminished the SOS response, whereas mannitol and glucose were ineffective. The results show that the net effect of H2O2-induced DNA damage is influenced by the balance of oxidative and antioxidative factors and, furthermore, can be modulated by constituents of the extracellular milieu.