Piper auritum ethanol extract is a potent antimutagen against food-borne aromatic amines. Mechanisms of action and chemical composition.

An ethanol extract of Piper auritum leaves (PAEE) inhibits the mutagenic effect of three food-borne aromatic amines (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP); 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx); 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) in the TA98 Salmonella typhimurium strain. Preincubation with MeIQx demonstrated in mutagenesis experiments that inhibition of Cytochrome P450 (CYP), as well as direct interaction between component(s) of the plant extract with mutagens, might account for the antimutagenic observed effect. Gas chromatography/mass spectrometry analysis revealed that safrole (50.7%), α-copaene (7.7%), caryophyllene (7.2%), ß-pinene (4.2%), γ-terpinene (4.1%) and pentadecane (4.1%) as the main components of PAEE. Piper extract and safrole were able to inhibit the rat liver microsomal CYP1A1 activity that participates in the amines metabolism, leading to the formation of the ultimate mutagenic/ molecules. According to this, safrole and PAEE inhibited MeIQx mutagenicity but not that of the direct mutagen 2-nitrofluorene. No mutagenicity of plant extract or safrole was detected. This study show that PAEE and its main component safrole are associate with the inhibition of heterocyclic amines activation due in part to the inhibition of CYP1A subfamily activity.

Neuroinflammation is able to downregulate cytochrome P450 epoxygenases 2J3 and 2C11 in the rat brain.

Cytochrome P450 (CYP) epoxygenases have been considered the main producers of epoxyeicosatrienoic acids (EETs) through the oxidation of arachidonic acid (AA). EETs display various biological properties, notably their powerful anti-inflammatory activities. In the brain, EETs have proven to be neuroprotective and to improve neuroinflammation. However, it is known that inflammation could modify CYP expression. We have previously reported that an inflammatory process in astrocytes is able to down-regulate CYP2J3 and CYP2C11 mRNA, protein levels, and activity (Navarro-Mabarak et al., 2019). In this work, we evaluated the effect of neuroinflammation in protein expression of CYP epoxygenases in the brain. Neuroinflammation was induced by the intraperitoneal administration of LPS (1 mg/kg) to male Wistar rats and was corroborated by IL-6, GFAP, and Iba-1 protein levels in the cortex over time. CYP2J3 and CYP2C11 protein levels were also evaluated in the cortex after 6, 12, 24, 48, and 72 h of LPS treatment. Our results show for the first time that neuroinflammation is able to downregulate CYP2J3 and CYP2C11 protein expression in the brain cortex.

Reduction in CYP1A1 and 2B2 activity at low oxygen tension.

The Cytochrome P450 (CYP) enzyme family comprises a wide array of monooxygenases involved in the oxidation of endobiotic and xenobiotic molecules. The active site of a CYP enzyme contains an iron protoporphyrin center coordinated to a cysteine thiolate, and then, molecular oxygen is associated with the iron to be converted into dioxygen complex plus substrate. Reduction by CYP reductase expedites hydroxylation of the compound. In this oxidation reaction, insufficient oxygen molecules would affect enzyme catalysis. Nevertheless, biochemical data about CYP kinetics at low oxygen concentrations are not available. In this work, we present the results on the variation in rat liver microsomal CYP Vmax app and Km app under normal and hypoxic conditions. Using alkoxyresorufin molecules as substrates, the Vmax/Km ratios for resorufin production decreased from 426 to 393 for CYP1A1 and from 343 to 202 for CYP2B1 at a low oxygen concentration (4.1 ppm) compared to the ratios observed at a normal oxygen concentration (6.5 ppm). Additionally, the bacterial mutagenicity of 2-aminoanthracene and cyclophosphamide, decreased by 32% and 42%, respectively, at low oxygen concentrations. These results support the hypothesis that low oxygen availability is implicated in the low efficiency of substrate oxidation by CYP.

Role of epoxyeicosatrienoic acids in the lung.

Epoxyeicosatrienoic acids (EETs) are synthetized from arachidonic acid by the action of members of the CYP2C and CYP2J subfamilies of cytochrome P450 (CYPs). The effects of EETs on cardiovascular function, the nervous system, the kidney and metabolic disease have been reviewed. In the lungs, the presence of these CYPs and EETs has been documented. In general, EETs play a beneficial role in this essential tissue. Among the most important effects of EETs in the lungs are the induction of vasorelaxation in the bronchi, the stimulation of Ca2+-activated K+ channels, the induction of vasoconstriction of pulmonary arteries, anti-inflammatory effects induced by asthma, and protection against infection or exposure to chemical substances such as cigarette smoke. EETs also participate in tissue regeneration, but on the downside, they are possibly involved in the progression of lung cancer. More research is necessary to design therapies with EETs for the treatment of lung disease.

Antimutagenic and antioxidant activity of the essential oils of Citrus sinensis and Citrus latifolia.

The essential oils of Citrus sinensis and Citrus latifolia showed antimycotic activity against Candida spp. isolated from the oral cavity; they are neither mutagenic on the Ames test nor cytotoxic. Their main components are R-(+)-limonene, ß-thujene, α-myrcene and γ-terpinene. The aim of this work was to evaluate their antimutagenic and antioxidant capacities. Antimutagenic properties were evaluated against MNNG and ENNG on S. typhimurium TA100; against 2AA on strain TA98 and in front of 4NQO and NOR on strain TA102. Both were antimutagenic against MNNG (p < 0.001) but only C. latifolia was antimutagenic against ENNG (p < 0.001). Both presented antimutagenic activity against 2AA (p < 0.001). They were antioxidant against the ROS-generating compound 4NQO (p < 0.001) and the antibiotic NOR (p < 0.001). In the antioxidant evaluation, the activity in DPPH assay was in a range of 6-23% for C. sinensis and of 22-71% for C. latifolia. Both were antioxidant compared with BHT in ß-carotene bleaching assay and were able to decreased apoptosis in HaCat cells stimulated with H2O2. The levels of intracellular superoxide ion were lower in the presence of both oils. In conclusion, the essential oils of C. sinensis and C. latifolia are antimutagenic against at least three types of mutagens and have antioxidants properties.

Modulation of the rat hepatic cytochrome P4501A subfamily using biotin supplementation.

Studies have found that biotin favors glucose and lipid metabolism, and medications containing biotin have been developed. Despite the use of biotin as a pharmacological agent, few studies have addressed toxicity aspects including the possible interaction with cytochrome P450 enzyme family. This study analyzed the effects of pharmacological doses of biotin on the expression and activity of the cytochrome P4501A subfamily involved in the metabolism of xenobiotics. Wistar rats were treated daily with biotin (2 mg/kg, i.p.), while the control groups were treated with saline. All of the rats were sacrificed by cervical dislocation after 1, 3, 5, or 7 days of treatment. CYP1A1 and CYP1A2 mRNAs were modified by biotin while enzyme activity and protein concentration were not affected. The lack of an effect of biotin on CYP1A activity was confirmed using other experimental strategies, including (i) cotreatment of the animals with biotin and a known CYP1A inducer; (ii) the addition of biotin to the reaction mixtures for the measurement of CYP1A1 and CYP1A2 activities; and (iii) the use of an S9 mixture that was prepared from control and biotin-treated rats to analyze the activation of benzo[a]pyrene (BaP) into mutagenic metabolites using the Ames test. The results suggest that biotin does not influence the CYP1A-mediated metabolism of xenobiotics.

Evaluation of genotoxicity and DNA protective effects of mangiferin, a glucosylxanthone isolated from Mangifera indica L. stem bark extract.

Mangiferin is a glucosylxantone isolated from Mangifera indica L. stem bark. Several studies have shown its pharmacological properties which make it a promising candidate for putative therapeutic use. This study was focused to investigate the in vitro genotoxic effects of mangiferin in the Ames test, SOS Chromotest and Comet assay. The genotoxic effects in bone marrow erythrocytes from NMRI mice orally treated with mangiferin (2000 mg/kg) were also evaluated. Additionally, its potential antimutagenic activity against several mutagens in the Ames test and its effects on CYP1A1 activity were assessed. Mangiferin (50-5000 µg/plate) did not increased the frequency of reverse mutations in the Ames test, nor induced primary DNA damage (5-1000 µg/mL) to Escherichia coli PQ37 cells under the SOS Chromotest. It was observed neither single strand breaks nor alkali-labile sites in blood peripheral lymphocytes or hepatocytes after 1h exposition to 10-500 µg/mL of mangiferin under the Comet assay. Furthermore, micronucleus studies showed mangiferin neither induced cytotoxic activity nor increased the frequency of micronucleated/binucleated cells in mice bone marrow. In short, mangiferin did not induce cytotoxic or genotoxic effects but it protect against DNA damage which would be associated with its antioxidant properties and its capacity to inhibit CYP enzymes.

Bergamottin is a competitive inhibitor of CYP1A1 and is antimutagenic in the Ames test.

Grapefruit juice (GJ) is a well known Cytochrome P450 (CYP) inhibitor; CYP3A is one of the most affected subfamily leading to anticarcinogenic and antimutagenic effects when GJ is administered to experimental animals in combination with mutagenic/carcinogenic agents metabolized by CYP3A. Bergamottin, naringin and dihydroxybergamottin are three main constituents contained within GJ and their inhibitory effect against CYP3A4 has been well documented. Reports suggest that CYP3A is not the only one affected but CYP1A and 2B are also affected by GJ. To explore this last possibility in depth we tested the in vitro capacity of bergamottin, naringin and dihydroxybergamottin to inhibit the activity of CYP1A and 2B subfamilies and found that bergamottin showed the strongest inhibitory effect and naringin showed no inhibition at all. Therefore, we decided to biochemically characterize the inhibitory properties of bergamottin. CYP1A1 Supersome® used in this study showed a Km(app)=0.0723 µM and a Vm(app)=6.141 µU/pmol with substrate ethoxyresorufin, and the biochemical characterization of bergamottin CYP1A1 inhibitory effect revealed that it is a competitive inhibitor with a Ki=10.703 nM. We also confirmed the antimutagenicity of this compound against the mutagenic effect of 3-methylcholanthrene and benzo[a]pyrene in the Ames test.

The antigenotoxic effects of grapefruit juice on the damage induced by benzo(a)pyrene and evaluation of its interaction with hepatic and intestinal Cytochrome P450 (Cyp) 1a1.

We determined the capacity of grapefruit juice (GJ) to inhibit the rate of micronucleated polychromatic erythrocytes (MNPE) in mice treated with benzo(a)pyrene (BaP), an environmental contaminant that is biotransformed by Cyp1a1 and is a strong genotoxic agent. For this study, we administered 4.1, 20.8, and 41.6 µl/g body weight (b.w.) of GJ to BaP-treated mice (340 mg/kg). We found a significant decrease in the frequency of MNPE at 48 and 72 h compared to BaP-only treated animals. In turn, no prevention of the cytotoxic damage induced by BaP was found. We next explored whether GJ's antigenotoxic mechanism of action was related to an inhibitory effect on the activity of the Cyp1a1 enzyme. A reduction in microsomal hepatic and intestinal ethoxyresorufin-O-deethylase (EROD) activity of 20% and 44%, respectively, was found in mice treated with BaP and GJ compared to BaP-only treated animals. Furthermore, when EROD inhibition was tested in vitro, we found a concentration-dependent EROD inhibition by GJ, which reached 85% of the maximum level. Together, these results suggest that the protective effect of GJ against the genotoxicity of BaP may be related to the inhibition of Cyp1a1 enzyme activity.

Correlation of the genotoxic activation and kinetic properties of Salmonella enterica serovar Typhimurium nitroreductases SnrA and cnr with the redox potentials of nitroaromatic compounds and quinones.

Bacterial nitroreductases (NRs) catalyse the oxygen-insensitive reduction of several nitro-substituted compounds and quinones. SnrA and cnr NRs have been previously identified in Salmonella enterica serovar Typhimurium; they reduce several environmental nitro compounds that display mutagenic activity in the Ames test. Although some of their biochemical properties have been reported, the substrate specificity of each protein over mutagenic nitro compounds is unknown; even more, the possible relationship between their capacity to activate nitro compounds into mutagens and the redox properties of putative substrates has been poorly investigated. We have purified SnrA and cnr and investigated their capacity to activate several mutagens in the Ames test as well as their kinetic parameters K(m) and V(max). Our results show that SnrA and cnr are able to activate 2,7-dinitrofluorene with the same efficiency and a similar mutagenic potency in the YG7132 tester strain; 1-nitropyrene and 1,3-dinitropyrene were efficiently activated by cnr, whereas 1,8-dinitropyrene, 1,6-dinitropyrene and 2-nitrofluorene were scarcely activated by either NR. The mutagenic potency of nitro compounds obtained in the presence of either enzyme correlates with their redox potential reported in the literature. On the other hand, a good correlation was obtained between the catalytic efficiency (V(max)/K(m)) of the purified cnr with the redox potential of eight molecules including nitro-substituted compounds and quinones. No correlation between redox potential and catalytic efficiency by SnrA was observed, suggesting that factors other than redox potential such as the structure of the compounds are involved in the catalytic efficiency of SnrA.

Nitrocompound activation by cell-free extracts of nitroreductase-proficient Salmonella typhimurium strains.

A characterization of nitrocompounds activation by cell-free extracts (CFE) of wild-type (AB(+)), SnrA deficient (B(+)), Cnr deficient (A(+)) and SnrA/Cnr deficient (AB(-)) Salmonella typhimurium strains has been done. The Ames mutagenicity test (S. typhimurium his(+) reversion assay) was used, as well as nitroreductase (NR) activity determinations where the decrease in absorbance generated by nitrofurantoin (NFN) reduction and NADP(H) oxidation in the presence of NFN, nitrofurazone (NFZ), metronidazole (MTZ) and 4-nitroquinoline-1-oxide (4NQO) were followed. Different aromatic and heterocyclic compounds were tested for mutagenic activation: 2-nitrofluorene (2-NF); 2,7-dinitrofluorene (2,7-DNF); 1-nitropyrene (1-NP), 1,3-dinitropyrene (1,3-DNP); 1,6-dinitropyrene (1,6-DNP); and 1,8-dinitropyrene (1,8-DNP). Differential mutagenicity was found with individual cell free extracts, being higher when the wild type or Cnr containing extract was used; nevertheless, depending on the nitrocompound, activation was found when either NR, SnrA or Cnr, were present. In addition, all nitrocompounds were more mutagenic after metabolic activation by CFE of NR proficient strains, although AB(-) extract still showed activation capacity. On the other hand, NR activity was predominantly catalyzed by wild type CFE followed by A(+), B(+) and AB(-) extracts in that order. We can conclude that results from the Ames test indicate that Cnr is the major NR, while NFN and NFZ reductions were predominantly catalyzed by SnrA. The characterization of the residual NR activity detected by the mutagenicity assay and the biochemical determinations in the AB(-) CFE needs further investigation.

The effect of aspartame on rat brain xenobiotic-metabolizing enzymes.

This study demonstrates that chronic aspartame (ASP) consumption leads to an increase of phase I metabolizing enzymes (cytochrome P450 (CYP)) in rat brain. Wistar rats were treated by gavage with ASP at daily doses of 75 and 125 mg/kg body weight for 30 days. Cerebrum and cerebellum were used to obtain microsomal fractions to analyse activity and protein levels of seven cytochrome P450 enzymes. Increases in activity were consistently found with the 75 mg/kg dose both in cerebrum and cerebellum for all seven enzymes, although not at the same levels: CYP 2E1-associated 4-nitrophenol hydroxylase (4-NPH) activity was increased 1.5-fold in cerebrum and 25-fold in cerebellum; likewise, CYP2B1-associated penthoxyresorufin O-dealkylase (PROD) activity increased 2.9- and 1.7-fold respectively, CYP2B2-associated benzyloxyresorufin O-dealkylase (BROD) 4.5- and 1.1-fold, CYP3A-associated erythromycin N-demethylase (END) 1.4- and 3.3-fold, CYP1A1-associated ethoxyresorufin O-deethylase (EROD) 5.5- and 2.8-fold, and CYP1A2-associated methoxyresorufin O-demethylase (MROD) 3.7- and 1.3-fold. Furthermore, the pattern of induction of CYP immunoreactive proteins by ASP paralleled that of 4-NHP-, PROD-, BROD-, END-, EROD- and MROD-related activities only in the cerebellum. Conversely, no differences in CYP concentration and activity were detected in hepatic microsomes of treated animals with respect to the controls, suggesting a brain-specific response to ASP treatment.

In vitro genotoxic evaluation of three alpha-asarone analogues.

alpha-Asarone has shown a significant capacity to reduce the level of lipids, including cholesterol. However, several toxic and genotoxic studies have determined that its use may pose a risk to human health. Therefore, a series of compounds structurally analogous to alpha-asarone were prepared in order to maintain the same pharmacological properties but with low toxicity. In this study we evaluated the potential of three alpha-asarone analogues to induce mutagenicity using the Ames test (strains TA98 and TA100 in the presence of metabolic activation), as well as the induction of sister chromatid exchanges (SCE) in cultured human lymphocytes. The tested compounds were: 1-(2,4,5-trimethoxyphenyl)propan-1-one (D1), 1-(2-chloro-4,5-dimethoxyphenyl)propan-1-one (D2), and 1-(4,5-dimethoxy-2-nitrophenyl)propan-1-ol (D3). The results in the first assay showed no mutagenic effect for the three tested analogues; in the TA100 strain, certain cytotoxicity did appear in the case of D2 and D3 only at high concentrations. In regard to the SCE assay, compounds D1 and D2 presented no statistical differences in comparison with the control culture values; however, the high dose of D3 (300 microg/ml) produced a significant increment in SCE (68% above the control value). With respect to the mitotic index and the cellular proliferation kinetics, we observed a reduction when compounds D2 and D3 were used at the higher concentrations. Our results encourage further preclinical studies of these compounds in both in vitro and in vivo models (particularly for analogues D1 and D2), to determine their toxicological profile and establish the possibility of using them in humans.

Cytochrome P450 expression in rat gastric epithelium with intestinal metaplasia induced by high dietary NaCl levels.

Drug metabolizing enzymes like cytochrome P450 (CYP) play an important role in determining the susceptibility of organs or tissue to the toxic effects of drugs or other xenobiotics. There is some evidence indicating that individual isoforms of CYPs are over-expressed in different types of malignant tumors including that of oesophagus, pancreas, breast, lung, colon and stomach. Nevertheless, it is not clear if this change in expression is previous or after the appearance of malignancy. This is important in order to clarify the possible role of xenobiotics in the development of gastric cancer. On the other hand, it has been reported that a high salt ingestion leads to histological changes in rat stomach mucosa including enhanced cell proliferation, lipid peroxidation and intestinal metaplasia. The aim of this study is to explore the expression and activity of CYP families involved in the metabolism of carcinogens in normal rat stomach mucosa and intestinal metaplasia induced by high NaCl ingestion. Male Wistar rats were exposed to diets containing different NaCl concentrations (0.6% control group, 6%, 12%, 18% and 24%) for 12 weeks and histological changes as well as CYP modulation were monitored in gastric mucosa. Chronic gastritis, regenerative hyperplasia and focal metaplasia were noted in animals receiving the 12%, 18% and 24% NaCl diets. In the same groups, induction of CYP1A1 and CYP3A2 was produced, mainly in areas of metaplasia. The expression of xenobiotic metabolizing enzymes in the gastric mucosa might contribute to chemical activation in the stomach, metabolizing both exogenous and endogenous compounds implicated in the development of gastric cancer.

Biomedical properties of saffron and its potential use in cancer therapy and chemoprevention trials.

INTRODUCTION: Chemoprevention strategies are very attractive and have earned serious consideration as potential means of controlling the incidence of cancer. An important element of anticancer drug development using plants is the accumulation and analysis of pertinent experimental data and purported ethnomedical (folkloric) uses for plants. The aim of this review is to provide an updated overview of experimental in vitro and in vivo investigations focused on the anticancer activity of saffron (Crocus sativus L.) and its principal ingredients. Potential use of these natural agents in cancer therapy and chemopreventive trials are also discussed. METHODS: A computerized search of published articles was performed using the MEDLINE database from 1990 to 2004. Search terms utilized including saffron, carotenoids, chemoprevention, and cancer. All articles were obtained as reprints from their original authors. Additional sources were identified through cross-referencing. RESULTS: Studies in animal models and with cultured human malignant cell lines have demonstrated antitumor and cancer preventive activities of saffron and its main ingredients, possible mechanisms for these activities are discussed. More direct evidence of anticancer effectiveness of saffron as chemopreventive agent may come from trials that use actual reduction of cancer incidence as the primary endpoint CONCLUSIONS: This work suggests that future research be warranted that will define the possible use of saffron as effective anticancer and chemopreventive agent in clinical trials.

Antigenotoxic and antioxidant effect of grapefruit juice in mice treated with daunorubicin.

Grapefruit juice (GJ) is widely consumed in many countries. Several of its constituents possess nutritive value, as well as antigenotoxic and antioxidant effects. Therefore, the aim of this investigation was to evaluate the capacity of GJ to inhibit the micronucleated polychromatic erythrocytes (MNPE) produced by daunorubicin (Dau) in an acute assay in mice, as well as to determine its antioxidant potential in mouse hepatic microsomes, and its capacity to trap free radicals in vitro. In regard to the first point, GJ produced no toxic or genotoxic damage; on the contrary, it generated a significant reduction of the MNPE formed by Dau. The effect was found throughout the examined schedule (from 24 to 96 h). The two high doses produced inhibition of about 60% at 48 h, 86% at 72 h and 100% at 96 h after the treatment. With respect to the GJ antioxidant potential, a 50% decrease in liver microsomal lipid peroxidation produced by Dau was found by quantifying malondialdehyde formation. Finally, a strong GJ scavenging activity evaluated with the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) was observed, giving rise to a concentration-dependent curve with a correlation coefficient of 0.98. Overall, our results established an efficient anticlastogenic potential of GJ, probably related to its antioxidant capacity, or to alterations of Dau metabolism, suggesting the pertinence of extending research on the matter using other mutagens and biological models.

Use of in vitro assays to assess the potential antigenotoxic and cytotoxic effects of saffron (Crocus sativus L.).

Saffron is harvested from the dried, dark red stigmas of Crocus sativus L. flowers. It is used as a spice for flavoring and coloring food and as a perfume. It is often used for treating several diseases. We assessed the antimutagenic, comutagenic and cytotoxic effects of saffron and its main ingredients using the Ames/Salmonella test system, two well known mutagens (BP, 2AA), the in vitro colony formation assay and four different cultured human normal (CCD-18Lu) and malignant (HeLa, A-204 and HepG2) cells. When only using the TA98 strain in the Ames/Salmonella test system, saffron showed non-mutagenic, as well as non-antimutagenic activity against BP-induced mutagenicity, and demonstrated a dose-dependent co-mutagenic effect on 2-AA-induced mutagenicity. The saffron component responsible for this unusual comutagenic effect was safranal. In the in vitro colony formation test system, saffron displayed a dose-dependent inhibitory effect only against human malignant cells. All isolated carotenoid ingredients of saffron demonstrated cytotoxic activity against in vitro tumor cells. Saffron crocin derivatives possessed a stronger inhibitory effect on tumor cell colony formation. Overall, these results suggest that saffron itself, as well as its carotenoid components might be used as potential cancer chemopreventive agents.

Modulation of rat liver cytochrome P450 by protein restriction assessed by biochemical and bacterial mutagenicity methods [corrected].

Protein restriction (PR) significantly inhibits spontaneous and chemical carcinogenesis. Several factors seem to be involved in this effect, including a decrease in body weight, cellular proliferation and DNA damage and an increase in antioxidant defenses. The current study was designed to determine modifications in some hepatic cytochromes P450 (CYPs) due to a hypoproteic diet and to investigate its implications on chemical mutagenesis. Western blot analysis showed decreases of 73, 40 and 74% in CYP1A, CYP2B and CYP2E1 protein concentrations in hepatic microsomes from animals fed a protein-restricted (6% protein) diet for 6 weeks in comparison with microsomes from rats fed a 24% protein diet during the same period. In the same way, low protein fed animals showed a 3.5-fold decrease in hepatic CYP1A1-associated ethoxyresorufin O-deethylase activity, a 6-fold decrease in CYP1A2-associated methoxyresorufin O-demethylase activity, a 1.7-fold decrease in CYP2B1-associated penthoxyresorufin O-dealkylase activity, a 9-fold decrease in CYP2B2-associated benzyloxyresorufin O-dealkylase and, finally, a 3.4-fold decrease in CYP2E1-associated 4-nitrophenol hydroxylase activity. As a result of decreased CYP hepatic protein concentrations and enzymatic activities, liver S9 from rats fed a hypoproteic diet was less efficient in activating promutagens than S9 prepared from rats fed a 24% protein diet in the Ames test. Mutagenic potency obtained with protein-restricted S9 was reduced 25-fold for 2-aminoanthracene, 1.5-fold for N-nitrosodipropylamine, 12.5-fold for N-nitrosodibutylamine, 2-fold for cyclophosphamide and N-nitrosopyrrolidine and 71-fold for N-nitrosodimethylamine. However, the mutagenic potency of benzo[a]pyrene was the same (4 revertants/ microg) with S9 derived from rats fed either a 6 or 24% protein diet.

Metabolic activation of three arylamines and two organophosphorus insecticides by coriander (Coriandrum sativum) a common edible vegetable.

Organophosphorus insecticides and arylamines, widely distributed in the environment, can be activated into mutagens by plants. Plant activation of three aromatic amines, 4-nitro-o-phenylenediamine (NOP), m-phenylenediamine (m-PDA) and 2-aminofluorene (2AF), and two organophosphorus insecticides, dimethoate and methyl parathion has been the focus of this study. The plant cell/microbe coincubation assay was used employing coriander (Coriandrum sativum) suspended cell cultures as the activating system. Interestingly, this vegetable is included in the Mexican diet and ingested generally uncooked and could have epidemiological consequences. As a genetic end point, the Salmonella typhimurium tester strain TA98 was used. Protein contents, as well as peroxidase activity and peroxidase activity inhibited by diethyldithiocarbamate (DEDTC) of coriander cultures were determined after the coculture. Coriander cells highly activated three aromatic amines, NOP, m-PDA and 2-AF to mutagenic products detected in Salmonella. On the other hand, insecticides were only lightly activated, probably because peroxidase activity of coriander cells was inhibited, corroborated by DEDTC peroxidase inhibition. In all the assays, NOP was the more potent mutagenic compound. The results demonstrated that coriander cells were metabolically competent and suitable for a plant cell microbe coincubation assay, developed to analyze the promutagen activation by plant systems and can be used as a indicator of potential genetic effects.