Genotoxic activity of 3-[3-phenyl-1,2,4-oxadiazol-5-yl] propionic acid and its peptidyl derivatives determined by Ames and SOS response tests

Compounds derived from 1,2,4-oxadiazole have being reported for their anti-inflamatory activity. However, those compounds should be devoid of any genotoxic side effect. In this work, the genotoxic activity of peptidomimetic moiety-containing 1,2,4-oxadiazoles derivatives was tested based on the Ames and SOS Chromotest. The results showed no mutagenic activity on the Ames test for 3-[3-phenyl-1,2,4-oxadiazol-5-yl] propionic acid (POPA) parental drug, but a weak SOS response induction on Chromotest. The chemical modifications reduced that response to a non-significative level, with l-phenylalanine peptidomimetic derivative being showing the lowest induction response. The results pointed out for the effectiveness of promoting chemical modifications of biological active compounds to increase its mode of action, showed in previous work, without increasing and even decreasing its DNA damage effect.     

Detection of ionizing radiations with the SOS Chromotest, a bacterial short-term test for genotoxic agents

The effects of 3 types of ionizing radiation, gamma-rays, neutrons and accelerated alpha-particles, were examined using the SOS Chromotest, a bacterial colorimetric assay for genotoxic agents based on the measurement of the SOS response in Escherichia coli. The SOS Chromotest appeared to be a sensitive and simple assay to detect quantitatively these radiations as well as their biological effects. The range of adsorbed doses for which induction was observed was similar for the 3 types of radiation, the minimum inducing doses being in the order of 2.5-5 Gy. We discuss the possible use of these observations to study the molecular action of radiations and to compare their genotoxic effects with those of chemicals.     

The Escherichia coli K-12 SOS chromotest agar spot test for simple, rapid detection of genotoxic agents

The Escherichia coli K-12 SOS chromotest is a colorimetric (beta-galactosidase induction) system for detecting genotoxic chemicals as agents which induce filamentation in response to DNA damage. The chromotest was modified from a liquid suspension assay to a simple, convenient agar spot test, which was performed in the manner of a related colorimetric prophage induction assay (BIA). Chromotest agar dishes yielded optimal results after 16-18 h incubation, presumably because of the agar growth characteristics of tester strain PQ37. Of 44 tested chemicals, nitro aromatics, cytotoxic/antitumor agents, polycyclic hydrocarbons and aflatoxins showed good activity. Alkylating agents such as MNNG and MMS were active only at high concentrations. Compounds active in both the chromotest and BIA were active at 10-100-fold lower concentrations in the chromotest. The chromotest appeared to be less effective than the Salmonella Ames mutagenicity test in the detection of diverse classes of chemical carcinogens. The chromotest may be a useful alternative to the BIA in the study of particular classes of genotoxic compounds.     

The SOS Chromotest, a colorimetric bacterial assay for genotoxins: validation study with 83 compounds

The SOS Chromotest is a simple bacterial colorimetric assay for genotoxicity. It is based on the measure of the induction of sfiA, a gene controlled by the general repressor of the SOS system in E. coli. Expression of sfiA is monitored by means of a gene fusion with lacZ, the structural gene for beta-galactosidase. We have examined 83 compounds of various chemical classes with the SOS Chromotest using a standard procedure. Comparison of the results with those obtained in the Mutatest (the Ames test) showed that most (90%) of the mutagenic compounds were also SOS inducers. For these compounds a quantitative correlation was observed between the mutagenic potency and the SOS-inducing potency (SOSIP). The case of the 10% remaining compounds giving conflicting results in the two tests is discussed. Sensitivity, specificity and accuracy for carcinogenicity prediction have been evaluated for the SOS Chromotest and the Mutatest using 73 chemicals for which carcinogenicity data were available. In spite of some differences, similar results were obtained in the two tests. The present data indicate that the SOS Chromotest has many practical advantages and may be used as a primary screening tool or as part of a battery of short-term tests for carcinogens.     

A comparative study of mutagenic and SOS-inducing activity of biphenyls, phenanthrenequinones and fluorenones

A total of 23 chemicals--biphenyls, phenanthrenequinones and fluorenones--were tested for mutagenicity towards Salmonella typhimurium strains TA1538, TA1535 and TA98. SOS-inducing activity of the same chemicals was studied in terms of the SOS-inducing potency in Escherichia coli PQ37, using an automated instrument controlled by a dedicated computer program for the SOS Chromotest. Of the 23 chemicals studied 14 induced His+ revertants in S. typhimurium TA1538 hisD305 (-1 frameshift); none induced His+ reversions in TA1535 (base-pair substitution). The mutagenicity of the chemicals in S. typhimurium TA98 (pKM 101) was lower than in TA1538. There was a close correlation between mutagenicity and SOS-inducing activity of fluorenones and phenanthrenequinones. None of the biphenyls tested induced SOS response and this property does not depend upon the mutagenic activity of the chemicals. SOS Chromotest is particularly valid in detecting chemicals which give rise to base-pair substitutions through SOS induction. If positive results are obtained, the Salmonella assay may be omitted. However, this test cannot replace the Ames test especially for the primary screening of mutagenicity of chemicals with unknown structure.     

Chemical composition and antigenotoxic properties of Lippia alba essential oils

The present work evaluated the chemical composition and the DNA protective effect of the essential oils (EOs) from Lippia alba against bleomycin-induced genotoxicity. EO constituents were determined by Gas Chromatography/Mass Spectrometric (GC-MS) analysis. The major compounds encountered being citral (33% geranial and 25% neral), geraniol (7%) and trans-β-caryophyllene (7%) for L. alba specimen COL512077, and carvone (38%), limonene (33%) and bicyclosesquiphellandrene (8%) for the other, COL512078. The genotoxicity and antigenotoxicity of EO and the compounds citral, carvone and limonene, were assayed using the SOS Chromotest in Escherichia coli. The EOs were not genotoxic in the SOS chromotest, but one of the major compound (limonene) showed genotoxicity at doses between 97 and 1549 mM. Both EOs protected bacterial cells against bleomycin-induced genotoxicity. Antigenotoxicity in the two L. alba chemotypes was related to the major compounds, citral and carvone, respectively. The results were discussed in relation to the chemopreventive potential of L. alba EOs and its major compounds.     

Toxicity and genotoxicity of surface water before and after various potabilization steps

Many studies have revealed the presence of compounds with genotoxic activity in drinking water by means of short-term mutagenicity tests. In this study, the influence of the different steps of surface water treatment on the mutagenicity of drinking water was evaluated. Four different types of samples were collected: raw lake water, water after pre-disinfection with chlorine dioxide, water after filtration on granular activated carbon, and tap water. Water extracts underwent a bacterial toxicity test (Microtox test) and different in vitro genotoxicity tests: a test with Salmonella typhimurium strains, a Saccharomyces cerevisiae test, the SOS Chromotest with Escherichia coli and the Mutatox test with Vibrio fischeri. The Microtox test revealed high toxicity in the treated water samples. The disinfection steps increased the toxicity: the Mutatox test confirmed these results and the Salmonella/microsome test at the highest doses showed toxicity that could conceal mutagenicity. The SOS Chromotest was positive in all treated water samples without metabolic activation. In the test with S. cerevisiae both toxicity and genotoxicity generally increased during the water treatment steps, especially in cells without induction of cytochrome P450.     

Induction of SOS and adaptive responses by alkylating agents in Escherichia coli mutants deficient in 3-methyladenine-DNA glycosylase activities

The induction of SOS and adaptive responses by alkylating agents was studied in Escherichia coli mutants tagA and alkA deficient in 3-methyladenine-DNA glycosylase activities. The SOS response was measured using an sfiA::lacZ operon fusion. The sfiA operon, in the double mutant tagA alkA, is induced at 5-50-fold lower concentrations of all tested methylating and ethylating compounds, as compared to the wild-type strain. In all cases, the tagA mutation, which inactivates the constitutive and specific 3-alkyladenine-DNA glycosylase I (TagI), sensitizes the strain to the SOS response. The sensitization effect of alkA mutation, which inactivates the inducible 3-alkyladenine-DNA glycosylase II (TagII), is observed under conditions which allow the induction of the adaptive response. We conclude that the persistence of 3-methyladenine and 3-ethyladenine residues in DNA most likely leads to the induction of the SOS functions. In contrast, the adaptive response, evaluated by O6-methylguanine-DNA methyltransferase activity in cell extracts, was not affected by either tagA or alkA mutations. The results suggest that the SOS and adaptive responses use different alkylation products as an inducing "signal". However, adaptation protein TagII inhibits the induction of the SOS response to some extent, due to its action at the level of signal production. Finally, we provide conditions to improve short-term bacterial tests for the detection of genotoxic alkylating agents.     

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

The genotoxic properties of nitrofurazone and furazolidone were studied using the Ames test and SOS-chromotest. Both compounds were found to act as strong mutagens on the TA97 and TA102 strains of S. typhimurium and to induce the SOS-repair system in the PQ37 strain of E. coli. A good concordance was found between the mutagenic activity and the ability to induce the SOS system. Ascorbic acid and sodium selenite only very slightly lowered the genotoxic effect of the 2 nitrofurans studied both in the Ames test and in the SOS-chromotest.     

Genotoxic, mutagenic and recombinogenic effects of rauwolfia alkaloids

In the last decade, the possible correlation between the use of reserpine and rauwolfia drugs as antihypertensive agents and breast cancer incidence has been investigated. For the purpose of evaluating the mutagenic and genotoxic effects of these drugs, reserpine and ajmalicine were studied using the SOS Chromotest and the induction of gene conversion, crossing-over and reverse mutation in the yeast diploid strain XS2316. The results indicated a lack of genotoxic, mutagenic and recombinogenic effects.     

Absence of genotoxic activity of refined smoke flavor (RSF) in two bacterial short-term tests

The genotoxic activities of refined smoke flavor (RSF) produced in Poland and used in food processing were investigated in 2 bacterial short-term tests. Its mutagenic activity was examined in the Salmonella/histidine plate assay and its SOS-inducing capacity in the SOS Chromotest both without and with 'activation' by a rat liver homogenate. No genotoxic activity was detected using these 2 bacterial tests.     

Study of the genotoxic potential of 48 inorganic derivatives with the SOS chromotest

The genotoxic potential of 48 inorganic derivatives was studied using the bacterial colorimetric assay: the SOS Chromotest. Some of these compounds are known as carcinogens (As, CR(VI), Cd, Ni) or suspected carcinogens for human beings (Hg, Pb), others are known as non-carcinogens. Among these 48 derivatives, only the two Cr(VI) compounds and the Sn(II) compounds gave positive results.     

Genotoxicity assessment of low-molecular weight interferon inducers by the SOS Chromotest

Tilorone and its aza-analogs, as well as CMA and its butyric analog (CNPA) were investigated as potential genotoxic agents by the SOS Chromotest. The SOS-inducing potency values (SOSIP) were 0.0033 and 0.0009 for SAF and vivakorfen, respectively, after activation with S9 fraction of mouse liver only. In contrast, an SOSIP value for tilorone of 0.0011 was observed in a non-activated assay. The SOSIPs of investigated compounds were low and comparable to the lowest values determined for other genotoxins. CMA and CNPA were not SOS inducers in any test system.     

Anti-genotoxic and free-radical scavenging activities of extracts from (Tunisian) Myrtus communis

The effect of extracts from leaves of Myrtus communis on the SOS reponse induced by Aflatoxin B1 (AFB1) and Nifuroxazide was investigated in a bacterial assay system, i.e. the SOS chromotest with Escherichia coli PQ37. Aqueous extract, the total flavonoids oligomer fraction (TOF), hexane, chloroform, ethyl acetate and methanol extracts and essential oil obtained from M. communis significantly decreased the SOS response induced by AFB1 (10 microg/assay) and Nifuroxazide (20 microg/assay). Ethyl acetate and methanol extracts showed the strongest inhibition of the induction of the SOS response by the indirectly genotoxic AFB1. The methanol and aqueous extracts exhibited the highest level of protection towards the SOS-induced response by the directly genotoxic Nifuroxazide. In addition to anti-genotoxic activity, the aqueous extract, the TOF, and the ethyl acetate and methanol extracts showed an important free-radical scavenging activity towards the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. These results suggest the future utilization of these extracts as additives in chemoprevention studies.     

Application of a semi-automated SOS chromotest for measuring genotoxicities of complex environmental mixtures containing polycyclic aromatic hydrocarbons.

Soxhlet-extracted samples of standard reference materials (SRMs) 1649 (PAR1: urban dust/organics) and 1650 (PAR2: diesel particulate matter) from the U.S. Institute of Standards and Technology were tested for induction of SOS functions using a semi-automated version of the SOS chromotest with Escherichia coli PQ37. Concentrations of 10 polycyclic aromatic hydrocarbons in the extracts were determined using reversed-phase HPLC. Only the diesel particulate matter (PAR2) extracts expressed SOS induction activity, which decreased when metabolic activation was used. Mutagenic PAH compounds (e.g., chrysene) were found in higher concentrations in the PAR2 extracts than in the PAR1 extracts but this could not explain the genotoxicity while it was mainly exhibited without metabolic activation. The direct genotoxic activity of the diesel particulate matter sample PAR2 is probably caused by nitroaromatic compounds; this was also supported by parallel studies with the Ames/Salmonella assay.     

Genotoxic activity of two furan analogues of benzo[a]pyrene and their 2-nitro derivatives

We measured the genotoxic activities in two bacterial tests, the Salmonella/histidine assay (a reverse mutation assay) and the SOS Chromotest (an assay for SOS induction in E. coli), of two pairs of isomeric furan analogues of benzo[a]pyrene: pyreno[1,2-b]furan (R7490) and pyreno[2,1-b]furan (R7692) and their 2-nitro derivatives, 8-nitro-pyreno[1,2-b]furan (R7489) and 8-nitro-pyreno[2,1-b]furan (R7691). We found that: For all 4 compounds, the responses were correlated in the two tests. For the 2-nitro derivatives, R7489 and R7691, the responses were extremely high, reaching SOS-inducing potencies of 5.2 X 10(3) and 10(5)/nmole in the SOS Chromotest and mutagenic potencies of 6.3 X 10(4) and 3.7 X 10(7) revertants/nmole in the Salmonella/histidine assay (strain TA98), respectively; the responses were only slightly decreased in nitroreductase-deficient strains. The responses to the two pyrenofurans were increased in the presence of an "activating mixture" but were still lower than that to benzo[a]pyrene. In contrast to benzo[a]pyrene and pyreno[2,1-b]furan (R7692), pyreno[1,2-b]furan (R7490) also gave a response in the absence of an "activating mixture". (5) Compounds with the oxygen heteroatom within the "bay region" gave lower responses than their isomers with the oxygen heteroatom outside the "bay region".     

Role of nitric oxide in the SOS response in Escherichia coli

Having one electron with unpaired spin, nitric oxide (NO) shows high reactivity and activates or inhibits free radical chain reactions. NO toxic and genotoxic effects appear to be the result of intracellular formation of peroxinitrite that can induce some cellular damages, including DNA strand breaks, DNA base oxidation, destruction of the key enzymes, etc. Taking into account the character of DNA damages being formed under NO activity, we proposed a formation of the SOS signal and induction the SOS DNA repair response in E. coli cells treated with NO physiological donors--DNIC and GSNO. The ability of NO donor compounds to induce the SOS DNA response in E. coli PQ37 with sfiA::lacZ operon fusion is reported here at the first time. So, the SOS DNA repair response induction is one of the function of nitric oxide.     

Genotoxic activity of 1,2,3‐triazolyl modified furocoumarins and 2,3‐dihydrofurocoumarins

The furocoumarin backbone is a promising platform for chemical modifications aimed at creating new pharmaceutical agents. However, the high level of biological activity of furocoumarins is associated with a number of negative effects. For example, some of the naturally occurring ones and their derivatives can show genotoxic and mutagenic properties as a result of their forming crosslinks with DNA molecules. Therefore, a particularly important area for the chemical modification of natural furocoumarins is to reduce the negative aspects of their bioactivity. By studying a group of 21 compounds—1,2,3‐triazolyl modified derivatives of furocoumarin and peucedanin—using the SOS chromotest, the Ames test, and DNA‐comet assays, we revealed modifications that can neutralize the structure's genotoxic properties. Theoretical aspects of the interaction of the compound library were studied using molecular modeling and this identified the leading role of the polyaromatic molecular core that takes part in stacking‐interactions with the pi‐systems of the nitrogenous bases of DNA.     

Genotoxicity of six pesticides by Salmonella mutagenicity test and SOS chromotest

Two in vitro tests (Ames test and SOS chromotest), one for bacterial mutagenicity and one for primary DNA damage, were assayed to determine the genotoxic activity of 6 pesticides (atrazine, captafol, captan, chlorpyrifosmethyl, molinate and tetrachlorvinphos). Assays were carried out both in the absence and presence of S9 fractions of liver homogenate from rat (Sprague–Dawley) pretreated with Aroclor 1254. Captan and captafol were genotoxic on both the Ames test and the SOS chromotest. Comparisons with mutagenesis data in Salmonella indicated that the SOS assay detected as genotoxic the pesticides that were mutagenic on the Salmonella test. Non-genotoxic effects were not detected in vitro either in the Salmonella/microsome assay nor in the SOS chromotest when bacterial tester strains were exposed to atrazine, molinate, chlorpyrifosmethyl and tetrachlorvinphos in the absence or presence of S9 mix.     

Using Short-Term Mutagenicity Tests for the Evaluation of Genotoxicity of Contaminated Soils

The study is aimed at evaluating the genotoxicity of contaminated soils using two bacterial mutagenicity assays — the Ames test and the SOS Chromotest. Initially, attention is directed at the method of extraction of soil samples by organic solvents. The detection of mutagenicity was dependent on the type of organic solvent. Dichloromethane (DCM) proved to be a better extraction agent than acetone because it is more effective for extracting mutagenic compounds. In the second part of our study, the possibilities of using bacterial mutagenicity assays for monitoring the course and effectiveness of bio-remediation of contaminated soils were ascertained. The results of an evaluation of the genotoxicity of a residue of polycyclic aromatic hydrocarbons (PAHs) that decompose with difficulty showed that a decrease in the concentration of detectable components need not always correspond to a total decrease of the mutagenic effect. Contaminants inducing SOS repair were degraded relatively quickly in soils, whereas it was found that mutagens inducing frameshift mutations persisted in samples.