N-Nitrosodiethylamine mutagenicity at low concentrations

Genotoxicity evaluation of nitrosamine impurities using human TK6 cells transduced with cytochrome P450s

Many nitrosamines are recognized as mutagens and potent rodent carcinogens. Over the past few years, nitrosamine impurities have been detected in various drugs leading to drug recalls. Although nitrosamines are included in a 'cohort of concern' because of their potential human health risks, most of this concern is based on rodent cancer and bacterial mutagenicity data, and there are little data on their genotoxicity in human-based systems. In this study, we employed human lymphoblastoid TK6 cells transduced with human cytochrome P450 (CYP) 2A6 to evaluate the genotoxicity of six nitrosamines that have been identified as impurities in drug products: N-nitrosodiethylamine (NDEA), N-nitrosoethylisopropylamine (NEIPA), N-nitroso-N-methyl-4-aminobutanoic acid (NMBA), N-nitrosomethylphenylamine (NMPA), N-nitrosodiisopropylamine (NDIPA), and N-nitrosodibutylamine (NDBA). Using flow cytometry-based assays, we found that 24-h treatment with NDEA, NEIPA, NMBA, and NMPA caused concentration-dependent increases in the phosphorylation of histone H2A.X (γH2A.X) in CYP2A6-expressing TK6 cells. Metabolism of these four nitrosamines by CYP2A6 also caused significant increases in micronucleus frequency as well as G2/M phase cell-cycle arrest. In addition, nuclear P53 activation was found in CYP2A6-expressing TK6 cells exposed to NDEA, NEIPA, and NMPA. Overall, the genotoxic potency of the six nitrosamine impurities in our test system was NMPA > NDEA ≈ NEIPA > NMBA > NDBA ≈ NDIPA. This study provides new information on the genotoxic potential of nitrosamines in human cells, complementing test results generated from traditional assays and partially addressing the issue of the relevance of nitrosamine genotoxicity for humans. The metabolically competent human cell system reported here may be a useful model for risk assessment of nitrosamine impurities found in drugs.

In vitro biochemical characterization and genotoxicity assessment of Sapindus saponaria seed extract

ETHNOPHARMACOLOGICAL RELEVANCE

Sapindus saponaria, also popularly known as soapberry, has been used in folk medicinal values because of its therapeutic properties and several compounds in its composition, which represent a target in potential for drug discovery. However, few data about its potential toxicity has been reported.

AIM OF THE STUDY

Plant proteins can perform essential roles in survival, acting as defense mechanism, as well functioning as important molecular reserves for its natural metabolism. The aim of the current study was to investigate the in vitro toxicity profile of protein extract of S. saponaria and detect protein potentially involved in biological effects such as collagen hydrolysis and inhibition of viral proteases.

MATERIALS AND METHODS

Protein extract of soapberry seeds was investigated for its cytotoxic and genotoxic action using the Ames test. The protein extract was also subjected to a partial purification process of a protease and a protease inhibitor by gel chromatography filtration techniques and the partially isolated proteins were characterized biochemically.

RESULTS

Seed proteins extract of S. saponaria was evaluated until 100 μg/mL concentration, presenting cytotoxicity and mutagenicity in bacterial model mostly when exposed to exogenous metabolic system and causing cytotoxic and genotoxic effects in HepG2 cells. The purification and partial characterization of a serine protease (43 kDa) and a cysteine protease inhibitor (32.8 kDa) from protein extract of S. Saponaria, corroborate the idea of ​​the biological use of the plant as an insecticide and larvicide. Although it shows cytotoxic, mutagenic and genotoxic effects.

CONCLUSION

The overall results of the present study provide supportive data on the potential use of proteins produced in S. saponaria seeds as pharmacological and biotechnological agents that can be further explored for the development of new drugs.

Carcinogenesis: Failure of resolution of inflammation?

Inflammation in the tumor microenvironment is a hallmark of cancer and is recognized as a key characteristic of carcinogens. However, the failure of resolution of inflammation in cancer is only recently being understood. Products of arachidonic acid and related fatty acid metabolism called eicosanoids, including prostaglandins, leukotrienes, lipoxins, and epoxyeicosanoids, critically regulate inflammation, as well as its resolution. The resolution of inflammation is now appreciated to be an active biochemical process regulated by endogenous specialized pro-resolving lipid autacoid mediators which combat infections and stimulate tissue repair/regeneration. Environmental and chemical human carcinogens, including aflatoxins, asbestos, nitrosamines, alcohol, and tobacco, induce tumor-promoting inflammation and can disrupt the resolution of inflammation contributing to a devastating global cancer burden. While mechanisms of carcinogenesis have focused on genotoxic activity to induce mutations, nongenotoxic mechanisms such as inflammation and oxidative stress promote genotoxicity, proliferation, and mutations. Moreover, carcinogens initiate oxidative stress to synergize with inflammation and DNA damage to fuel a vicious feedback loop of cell death, tissue damage, and carcinogenesis. In contrast, stimulation of resolution of inflammation may prevent carcinogenesis by clearance of cellular debris via macrophage phagocytosis and inhibition of an eicosanoid/cytokine storm of pro-inflammatory mediators. Controlling the host inflammatory response and its resolution in carcinogen-induced cancers will be critical to reducing carcinogen-induced morbidity and mortality. Here we review the recent evidence that stimulation of resolution of inflammation, including pro-resolution lipid mediators and soluble epoxide hydrolase inhibitors, may be a new chemopreventive approach to prevent carcinogen-induced cancer that should be evaluated in humans.

Nelumbo nucifera leaf extract treatment attenuated preneoplastic lesions and oxidative stress in the livers of diethylnitrosamine-treated rats

Lotus (Nelumbo nucifera Gaertn) possesses antioxidant, hepatoprotective, and anticancer potential. This study determined the protective role of aqueous extract from Nelumbo nucifera leaves (NLE) against N-diethylnitrosamine (DEN)-induced oxidative stress and hepatocellular carcinogenesis in a sample of Sprague-Dawley rats. NLE was fed orally to rats in which hepatic carcinoma was induced with DEN for 12 weeks. Five groups of 12 rats each were used for the study: Group I (control group) rats received distilled water; Group II rats were induced with DEN; Group III rats were induced with DEN and cotreated with 0.5% NLE; Group IV rats were induced with DEN and cotreated with 1.0% NLE; and Group V rats were induced with DEN and cotreated with 2.0% NLE. Clinical chemistry, organ weight, inflammatory marker, protein expression, enzyme, and antioxidant analyses were conducted. NLE administration to rats resulted in significantly decreased levels of serum alanine aminotransferase, aspartate aminotransferase, and albumin, which is indicative of hepatocellular damage, compared with the control group. DEN-induced oxidative stress was inhibited by NLE and this inhibition was paralleled by decreased lipid peroxides and increased glutathione transferase, superoxide dismutase, catalase, and glutathione peroxidase activity in liver tissues. The status of nonenzymatic antioxidants, such as reduced glutathione, was also found to be increased in NLE-administered rats. Furthermore, NLE decreased tumor size, hepatic Rac1, PKCα, and GSTπ expressions compared with the DEN-only group. Thus, supplementation of NLE reduced the adverse changes that occur because of liver cancer. These results prove that NLE protects against liver carcinogenesis induced because of treatment with DEN through blocking lipid peroxidation, hepatic cell damage, and enhancing the antioxidant defense system.

Mutagenic activities of biochars from pyrolysis

Biochar production, from pyrolysis of lignocellulosic feedstocks, agricultural residues, and animal and poultry manures are emerging globally as novel industrial and commercial products. It is important to develop and to validate a series of suitable protocols for the ecological monitoring of the qualities and properties of biochars. The highly sensitive Salmonella mutagenicity assays (the Ames test) are used widely by the toxicology community and, via the rat liver extract (S9), can reflect the potential for mammalian metabolic activation. We examined the Ames test for analyses of the mutagenic activities of dimethylsulphoxide (DMSO) extracts of biochars using two bacterial models (S. typhimurium strains TA98 and TA100) in the presence and in the absence of the metabolic activation with the S9-mix. Tester strain TA98 was most sensitive in detecting mutagenic biochar products, and the contribution of S9 was established. Temperature and times of pyrolysis are important. Biochar pyrolysed at 400°C for 10min, from a lignocellulose precursor was mutagenic, but not when formed at 800°C for 60min, or at 600°C for 30min. Biochars from poultry litter, and manures of calves fed on grass had low mutagenicities. Biochar from pig manure had high mutagenicity; biochars from manures of cows fed on a grass plus cereals, those of calves fed on mother's milk, and biochars from solid industrial waste had intermediate mutagenicities. The methods outlined can indicate the need for further studies for screening and detection of the mutagenic residuals in a variety of biochar products.

Modulatory efficacy of dieckol on xenobiotic-metabolizing enzymes, cell proliferation, apoptosis, invasion and angiogenesis during NDEA-induced rat hepatocarcinogenesis

Dieckol (DEK) is a major polyphenol of marine brown seaweed Ecklonia cava which is a potential candidate for cancer therapy. However, the underlying mechanism of DEK as an anticancer drug remains to be elucidated. In this study, we evaluated the molecular mechanisms involved in the chemopreventive efficacy of DEK in N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis rats by analyzing markers of xenobiotic-metabolizing enzymes (XMEs), apoptosis, invasion, and angiogenesis. Rats administered NDEA developed hepatocarcinogenesis that displayed apoptosis avoidance coupled to upregulation of pro-inflammatory, invasion, and angiogenesis markers. Treatment of DEK effectively suppressed the NDEA-initiated hepatocarcinogenesis by modulation of XMEs, inducing of apoptosis via the mitochondrial pathway as revealed by modulating the Bcl-2 family proteins, cytochrome C, caspases, and inhibiting invasion, and angiogenesis as evidenced by changes in the activities of MMPs (MMP2/9) and the expression of VEGF. In addition, DEK exerts its anticancer effects via inhibition of pro-inflammatory transcription factor NF-κB (nuclear factor κB) and COX2 in NDEA-induced hepatocarcinogenesis. Taken together, this study demonstrates that DEK modulates the expression of key molecules that regulate apoptosis, inflammation, invasion, and angiogenesis. These results strongly indicate that DEK from E. cava is an attractive candidate for chemoprevention.

Protective Role of Curcumin against N-Nitrosodiethylamine (NDEA)-Induced Toxicity in Rats

The present investigation was aimed at studying the possible role of curcumin against N-nitrosodiethylamine (NDEA)-induced toxicity in albino rats. Administration of NDEA to rats at a concentration of 0.1 mg/ml in drinking water ad libitum for 21 days produced toxicity in them, which was evident from histopathological changes in the rat livers, and increased levels of blood serum enzyme markers, i.e. aspartate transaminase, alanine transaminase, alkaline phosphatase, and lactate dehydrogenase. In addition, the levels of oxidative stress markers like lipid peroxidation (LPO), protein carbonyl (PCC), and glutathione-S-transferase (GST) activity were elevated and the total glutathione (GSH) content was reduced in the livers. The administration of curcumin to rats at concentrations of 10, 20, and 40 mg/ml in drinking water along with 0.1 mg/ml of NDEA for 21 days effectively suppressed NDEA-induced toxicity and also resulted in a dose-dependent reduction in the levels of blood serum enzyme markers (AST, ALT, ALP, and LDH). Moreover, LPO, PCC, and GST activity were reduced and the GSH level was increased upon the administration of curcumin along with NDEA. The results obtained for the comet assay in rat hepatocytes and blood lymphocytes showed a significant dose-dependent decrease in the mean tail length. The micronucleus assay performed on rat hepatocytes also showed a dose-dependent reduction in the frequency of micronucleated cells along with curcumin administration. These results suggest that curcumin has a protective role against NDEA-induced toxicity in albino rats.

Dose-dependent effect of N'-Nitrosodiethylamine on hepatic architecture, RBC rheology and polypeptide repertoire in Wistar rats

N'-Nitrosodiethylamine (NDEA) is an effective hepatotoxicant, carcinogen and mutagen. NDEA-induced hepatic necrosis, through metabolic activation by CYP2E1, is an extensively used experimental model. In the present study, we analysed the dose- and time-dependent effect of NDEA on hepatic damage, RBC rheology and proteomic profile in male Wistar rats. The rats, 5-6 weeks old, were divided into four groups: Group-1 served as control and received normal saline, Group-2 received a single dose of 200 mg/kg body weight NDEA intraperitoneally (i.p.) and the animals were sacrificed after one week; the rats of Group-3 received a single dose of 100 mg/kg body weight NDEA and were sacrificed after one week; Group-4 received 100 mg/kg body weight/wk NDEA for two weeks and were then sacrificed. Various biochemical parameters such as ALT, AST, ALP and bilirubin were determined. Further, RBC rheology, histopathology (H&E staining) of liver biopsies and polypeptide profiling (SDS-PAGE) in sera and liver sections were also carried out both in control and NDEA treated groups. Our results showed a significant increase in all the biochemical parameters of the liver function test (p<0.05). In NDEA treated categories dacryocytes (tear drop cells), schistocytes (fragmented cells), codocytes (target cells), acanthocytes (spur cells) and ovalocytes (oval cells) were observed. H & E stained liver biopsies treated with NDEA showed abnormal liver architecture with severe haemorrhage, neutrophilic infiltration and dysplastic hepatocytes manifested in a dose-dependent manner. Software analysis of SDS-PAGE of control and NDEA treated rat sera and liver revealed qualitative and quantitative differences in polypeptide composition. Based on the presence/absence, polypeptides were classified in three different categories: (1) house-keeping, present in all the groups investigated; (2) novel, present in either control or NDEA treated group at any given time; (3) differential expression, showing quantitative differences. Our study indicates a dose and time-dependent hepatocellular damage and proteome profile which is likely due to NDEA-mediated oxidative stress in rats.

Protective effect of Genistein against N-nitrosodiethylamine (NDEA)-induced hepatotoxicity in Swiss albino rats

In the present study, we studied the effect of Genistein against the hepatotoxicity induced by N-nitrosodiethylamine (NDEA). NDEA is present in almost all kinds of food stuff and has been reported to be a hepatocarcinogen. The male rats were exposed to NDEA (0.1 mg/mL) dissolved in drinking water separately and along with 25, 50, 100 mg/mL of Genistein for 21 days. The activities of serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were measured in blood serum. Lipid peroxidation, protein carbonyl content, micronucleus frequency and DNA damage (Comet assay) were performed on rat hepatocytes. The results of the study reveal that the treatment of NDEA along with Genistein showed a significant dose-dependent decrease in the levels of blood serum enzymes i.e., SGOT, SGPT, ALP and LDH (P<0.05). The HE staining of histological sections of the liver also revealed a protective effect of Genistein. A significant dose-dependent reduction in the lipid peroxidation and protein carbonyl content was observed in rats exposed to NDEA (0.1 mg/mL) along with Genistein (P<0.05). The results obtained for the comet assay in rat hepatocytes showed a significant dose-dependent decrease in the mean tail length (P<0.05). Thus the present study supports the hepatoprotective role of Genistein.

Anticarcinogenic effect of brucine in diethylnitrosamine initiated and phenobarbital-promoted hepatocarcinogenesis in rats

We evaluated the effects of brucine on N-nitrosodiethylamine (DENA)-induced hepatocarcinogenesis in rats. Initiation of hepatocarcinogenesis was done by intraperitoneal injection of diethylnitrosamine (DENA) followed by promotion with phenobarbital. The rats were exposed to dietary brucine for 4 weeks prior to initiation, and the treatment was continued for 22 consecutive weeks. Brucine decreased the incidence, total number, multiplicity, size and volume of preneoplastic hepatic nodules in a dose-dependent manner. Administration of DENA induced hepatocellular carcinoma (HCC), as evidenced by changes in histopathological architecture, increased activity of cytochrome P450, decreased activity of glutathione Stransferase (GST) as well as decreased antioxidant status, enhanced lipid peroxidation, increased liver marker enzymes. Western blot analysis showed decreased expression of cyclin D1 and Bcl-2 with activation of caspase-3 and increased expression of Bax. Immunohistochemical demonstrated the decreased expression of the PCNA and VEGF. These results indicate that brucine prevents lipid peroxidation and hepatic cell damage and also protects the antioxidant system in DENA-induced hepatocarcinogenesis.

Inhibitory effect of naringenin (citrus flavonone) on N-nitrosodiethylamine induced hepatocarcinogenesis in rats

We evaluated the effects of naringenin on N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in rats. Administration of NDEA induced hepatocellular carcinoma (HCC), as evidenced by changes in histopathological architecture, increased activity of cytochrome P450, decreased activity of glutathione S-transferase (GST) as well as decreased antioxidant status, enhanced lipid peroxidation and increased liver marker enzymes. Pre- and post-treatment with naringenin effectively suppressed NDEA-initiated hepatocarcinoma and the associated preneoplastic lesions by modulating xenobiotic-metabolizing enzymes (XMEs), alleviating lipid peroxidation (through both free radical scavenging and the enhanced antioxidant status), and decreased levels of liver marker enzymes. These results indicate that naringenin prevents lipid peroxidation and hepatic cell damage and also protects the antioxidant system in N-nitrosdithylamine-induced hepatocarcinogenesis.

In vitro and in vivo toxicological evaluation of extract and fractions from Baccharis trimera with anti-inflammatory activity

ETHNOPHARMACOLOGICAL RELEVANCE

Baccharis trimera (Less) DC. (Asteraceae), popularly known in Brazil as "carqueja", have been used in folk medicine to treat gastrointestinal, hepatic and renal diseases, and inflammatory processes as rheumatism.

AIM OF THE STUDY

To evaluate the in vitro and in vivo toxicological effects of anti-inflammatory Baccharis trimera aqueous extract and fractions.

MATERIALS AND METHODS

Aqueous extract of Baccharis trimera (AEBt) was produced by infusion in boiling water. After lyophylization AEBt was extracted with 80% ethanol, originating the ethanolic supernatant fraction (EFBt) and the aqueous sediment fraction (AFBt). Anti-inflammatory properties of AEBt, EFBt or AFBt (3, 30 or 300 μg/kg b.w.) were evaluated by the carrageenan-induced mouse paw edema using indomethacin (10mg/kg) as positive control. The growth of rat hepatoma cells (HTC) and human embryo kidney epithelial cells (HEK) was determined by protein staining assay. Cytotoxicity was assayed by the tetrazolium salt (MTT) reduction. Cyclosporin was used as reference cytotoxic drug for spleen cells and doxorubicin for HTC and HEK cells. For in vivo toxicological evaluation SW male mice were daily and oral (gavage) treated with extract/fractions at 4.2mg/kg or 42 mg/kg during 15 days. After treatment liver or kidney cells were submitted to comet assay to determine the DNA damage index, and the glutathione S-transferase activity was assayed towards ETHA (class Pi) and CDNB (several classes). Mutagenicity was evaluated by the Ames test using Salmonella typhimurium strains TA97, TA98, TA100, and TA102.

RESULTS

The anti-inflammatory effects of EFBt were higher than those of AEBt or AFBt. Mice treatment (3-300 μg/kg) with AFBt reduced the paw edema (3h) at lower levels (29.2-37.3%; P<0.01), than those observed for AEBt (44.7-54.2%; P<0.001), EFBt (49.3-58.2%; P<0.001) or indomethacin (64.6%, P<0.001, 10mg/kg). The growth of kidney cells (HEK) was inhibited by AEBt (IC(50) 182.6 μg/ml), EFBt (IC(50) 78.1 μg/ml) and AFBt (IC(50) 86.2 μg/ml), with lower effects on HTC hepatic cell (IC(50) 308.8 μg/ml, 396.5 μg/ml and 167.9 μg/ml, respectively). As evaluated by MTT test, AFBt exhibited cytotoxicity for HEK cells (IC(50) 372.5 μg/ml), but none for HTC ones; by the way, AFBt stimulated spleen cells (EC(50) 2.2 μg/ml) while cyclosporine, a cytotoxic reference drug inhibited them with IC(50) of 0.42 μg/ml; the IC(50) for doxorubicin for HEK and HTC cells was 0.28 μg/ml and 14.4 μg/ml, respectively, at 96h. No mutagenic potential was observed. Mice treatment with AEBt or AFBt at 42 mg/kg for 15 days altered the kidney relative weight, but not at 4.2mg/kg. Baccharis trimera did not change liver, spleen or popliteal lymph node relative weight. DNA damage index of kidney cells was observed on mice treated with AEBt/AFBt, but not on animals treated with EFBt, while DNA lesions were detected on liver cells only after AFBt treatment. The general activities of hepatic GST and Pi GST were reduced by EFBt and AFBt treatment, respectively.

CONCLUSIONS

Baccharis trimera did not show mutagenicity, inhibited the GST activity, a hepatic detoxification enzyme, and induced in vivo (genotoxicity) and in vitro toxicological effects to kidney cells.

Ability of Allium cepa L. root tips and Tradescantia pallida var. purpurea in N-nitrosodiethylamine genotoxicity and mutagenicity evaluation

N-nitroso compounds, such as N-nitrosodiethylamine (NDEA), can be formed by the reaction of secundary amines with nitrosating agents, and are suspected to be involved in tumors in humans. NDEA has been considered a weak carcinogen in genotoxic assays probably due to the inefficient nitrosamine activation system that is used and/or to the efficient repair system. In this work, we evaluated the sensibility of Allium cepa L. root tips and Tradescantia stamen hair mutation assay (Trad-SH) using Tradescantia pallida var. purpurea for NDEA (0.1; 0.5; 5 and 25mM) genotoxicity and mutagenicity induction. Allium cepa L. was treated with different NDEA concentrations for 3h, for 3 consecutive days, including negative control (distilled water) and positive control maleic hydrazide (MH 30mg/mL). After treatment, the roots were hydrolyzed, squashed, and the mitotic index (MI) and cytological abnormalities were scored. The results revealed a cytostatic effect of NDEA (0.5 and 5mM), showing a significant reduction in the MI. Chromosome stickiness suggests a NDEA toxic effect. T. pallida purpurea did not respond to mutagens with a dose-dependent pattern. In conclusion, our study indicates that the root tips of Allium cepa L. have sensibility to detect NDEA genotoxicity, but not for Trad-SH test.

Mutagenicity of Chinese traditional medicine Semen Armeniacae amarum by two modified Ames tests

Background

Semen armeniacae amarum (SAA) is a Chinese traditional medicine and has long been used to control acute lower respiratory tract infection and asthma, as a result of its expectorant and antiasthmatic activities. However, its mutagenicity in vitro and in vivo has not yet been reported. The Ames test for mutagenicity is used worldwide. The histidine contained in biological samples can induce histidine-deficient cells to replicate, which results in more his⁺ colonies than in negative control cells, therefore false-positive results may be obtained. So, it becomes a prerequisite to exclude the effects of any residual histidine from samples when they are assayed for their mutagenicity. Chinese traditional herbs, such as SAA, are histidine-containing biological sample, need modified Ames tests to assay their in vitro mutagenicity.

Methods

The mutagenicity of SAA was evaluated by the standard and two modified Ames tests. The first modification used the plate incorporation test same as standard Ames teat, but with new negative control systems, in which different amounts of histidine corresponding to different concentrations of SAA was incorporated. When the number of his⁺ revertants in SAA experiments was compared with that in new negative control, the effect of histidine contained in SAA could be eliminated. The second modification used a liquid suspension test similar to the standard Ames test, except with histidine-rich instead of histidine-limited medium. The aim of this change was to conceal the effect of histidine contained in SAA on the final counting of his⁺ revertants, and therefore to exclude false-positive results of SAA in the Ames test. Furthermore, the effect of SAA on chromosomal aberration in mammalian bone marrow cells was tested.

Results

The standard Ames test showed a positive result for mutagenicity of SAA. In contrast, a negative response was obtained with the modified plate incorporation and modified suspension Ames tests. Moreover, no apparent chromosomal aberrations were observed in mammalian bone marrow cells treated with SAA.

Conclusion

The standard Ames test was not suitable for evaluating the mutagenicity of SAA, because false-positive result could be resulted by the histidine content in SAA. However, the two modified Ames tests were suitable, because the experimental results proved that the effect of histidine in SAA and therefore the false-positive result were effectively excluded in these two modified Ames tests. This conclusion needs more experimental data to support in the future. Moreover, the experimental results illustrated that SAA had no mutagenicity in vitro and in vivo. This was in agreement with the clinical safety of SAA long-term used in China.

Protective role of dietary fibre on N-nitrosopyrrolidine-induced toxicity in hypercholesterolemic rats

N-nitrosopyrrolidine (NPYR) is an important carcinogen, frequently present in the environment and food chain. Oral administration of NPYR to experimental rats evoked severe biochemical and pathological changes. In the present investigation, the protective role of dietary fibre on NPYR-induced toxicity in hypercholesterolemic rats was studied. Supplementation of chickpea seed coat fibre in the diet reduced the hepato-toxic effects of NPYR, as evident from the decreased hepatic degeneration and improved liver weight index compared to control. Administration of NPYR resulted in an increase in the osmotic fragility of erythrocytes in the experimental animals. The antioxidant potential of experimental animals decreased in the NPYR-fed group, which was evident from the increased in vitro lipid peroxidation (LPO) of erythrocytes. However, chickpea seed coat fibre considerably reduced the peroxidative damage done by NPYR. Administration of NPYR resulted in a substantial and significant increase in LPO in all tissues, to a varying degree, though the effect was maximum in the case of the liver. Inclusion of chickpea seed coat fibre considerably reduced the peroxidative damage caused by NPYR in all tissues. The effect of NPYR administration on antioxidant potential was variable in different tissues, but the effect was reduced considerably on inclusion of chickpea seed coat fibre in the diet, providing reasonable protection against NPYR-induced oxidative stress, and, hence, its toxicity. Histopathological analysis of different tissues (heart, liver, lungs, spleen and kidneys) showed mild to severe pathological changes among the control and experimental groups. However, the pathological effects of NPYR administration were markedly reduced with the addition of chickpea seed coat fibre in the diet.

Genotoxic evaluation of extracts from Aplysina fulva, a Brazilian marine sponge

A range of biologically active secondary metabolites with pharmacological application has been reported to occur in marine sponges. The present study was undertaken to provide a set of data on the safety of a hydro-alcoholic extract (ALE) and an aqueous fraction (AQE) from Aplysina fulva Pallas, 1766 (Aplysinidae, Verongida, Porifera). Salmonella typhimurium strains TA97, TA98, TA100 and TA102, Escherichia coli strains PQ65, OG40, OG100, PQ35 and PQ37 and Balb/c 3T3 mouse fibroblasts were used to detect induction of DNA lesions by ALE and AQE. Assays used for these analyses were a bacterial (reverse) mutation assay (Ames test), the SOS-chromotest and the comet assay. Both extracts presented identical infrared 2-oxazolidone spectra. ALE treatment induced a higher frequency of type-4 comets, indicative of increasing DNA migration, in the alkaline comet assay. ALE also induced a weak genotoxic effect, as expressed by the induction factor (IF) values in the test with E. coli strain PQ35 (IF=1.5) and by cytotoxic effects in strains PQ35, PQ65 and PQ37. Positive SOS induction (IF=1.7) was detected in strain PQ37 treated with diluted AQE. No genotoxic effects were observed in strains PQ35, PQ65, OG40 and OG 100 after treatment with AQE dilutions. Using the bacterial (reverse) mutation test and survival assays with or without S9 mix, after 60min of pre-incubation, we observed for strain TA97 treated with ALE a weak mutagenic response (MI=2.2), while cytotoxic effects were seen for strains TA98, TA100 and TA102. AQE did not show mutagenic activity in any of the strains tested, but a weak cytotoxic effect was noted in strain TA102. Our data suggest that both ALE and AQE from A. fulva induce DNA breaks leading to cytotoxicity and mutagenicity under the conditions used.

Evaluation of nitroreductase and acetyltransferase participation in N-nitrosodiethylamine genotoxicity

N-Nitroso compounds, such as N-nitrosodiethylamine (NDEA), are a versatile group of chemical carcinogens, being suspected to be involved in gastrointestinal tumors in humans. The intestinal microflora can modify a wide range of environmental chemicals either directly or in the course of enterohepatic circulation. Nitroreductases from bacteria seem to have a wide spectrum of substrates, as observed by the reduction of several nitroaromatic compounds, but their capacity to metabolize N-nitroso compounds has not been described. To elucidate the participation of nitroreductase or acetyltransferase enzymes in the mutagenic activity of NDEA, the bacterial (reverse) mutation test was carried out with the strains YG1021 (nitroreductase overexpression), YG1024 (acetyltransferase overexpression), TA98NR (nitroreductase deficient), and TA98DNP6 (acetyltrasferase deficient), and YG1041, which overexpresses both enzymes. The presence of high levels of acetyltransferase may generate toxic compounds that must be eliminated by cellular processes or can lead to cell death, and consequently decrease the mutagenic effect, as can be observed by the comparison of strain TA98DNP6 with the strains TA98 and YG1024. The slope curves for TA98 strain were 0.66 rev/microM (R(2) = 0.51) and 52.8 rev/microM (R(2) = 0.88), in the absence and presence of S9 mix, respectively. For YG1024 strain, the slope curve, in the presence of S9 mix was 6897 rev/microM (R(2) = 0.78). Our data suggest that N-nitroso compounds need to be initially metabolized by enzymes such as cytochromes P450 to induce mutagenicity. Nitroreductase stimulates toxicity, while acetyltransferase stimulates mutagenicity, and nitroreductase can neutralize the mechanism of mutagenicity generating innoccuos compounds, probably by acting on the product generated after NDEA activation.

AFP gene expression after acute diethylnitrosamine intoxication is not Afr2 regulated

The level of alpha-fetoprotein (AFP) gene expression during liver regeneration in mice is regulated by the Afr2 gene. C3H/HeJ mice express 10-fold higher levels of AFP than C57BL/6J mice. We show that AFP gene expression is not Afr2 regulated after intoxication with the carcinogen diethylnitrosamine (DEN). Peak levels of AFP gene expression of the 2 strains were identical, although reached at different times following treatment. Analysis of the expression of AFP derived transgenes not subject to Afr2 regulation and genetic analyses showed that the difference in timing of peak AFP gene expression after DEN intoxication was independent of Afr2 regulation.

Participation of BER and NER pathways in the repair of DNA lesions induced at low N-nitrosodiethylamine concentrations

In the present work, we evaluated (p < 0.05) the participation of base excision repair (BER) and nucleotide excision repair (NER) mechanisms in repairing DNA lesions induced by N-nitrosodiethylamine (NDEA) at 1.5 ng/mL-36.5 microg/mL, through cell survival, in different single and double Escherichia coli DNA repair mutants (uvrA, uvrB, uvrC, fpg, nth, xthA, fpg/nth, uvrA/fpg, fpg/xthA, mutY, and fpg/mutY), using pre-incubation periods of 90 min. Mutant strains BH20 (fpg) and AB1886 (uvrA) showed microsomal enzyme (S9 mix) independent NDEA cytotoxicity. Cytotoxicity was also detected at lowest NDEA concentrations, in the presence of S9 mix, with strains BH980 (mutY) and BH990 (fpg/mutY). NDEA cytotoxicity, without S9 mix, was detected for mutant strains AB1884 (uvrC) and AB1885 (uvrB). Through SOS chromotest with 90 min of pre-incubation for uvrA and nth strains, only NER was shown to be required for repairing NDEA-induced lesions with or without metabolic activation. PQ37 and PQ66 strains, both uvrA mutants, showed different levels of NDEA sensitivity. The findings suggest that, under the used conditions, and at low concentrations, NDEA-induced lesions require both repair pathways.

Genotoxic evaluation of a vinifera skin extract that present pharmacological activities

Toxicity of an alcohol-free hydro-alcoholic grape skin extract (GSE) obtained from red grapes Vitis labrusca (Isabel varietal) that present antihypertensive, vasodilator and antioxidant effects was estimated by different bioassays. Using the Salmonella/microsome assay for strains TA97, TA98, TA100 and TA102 no mutagenicity was detected for all tested concentrations (0.1-100 microg/ml), even with metabolization. Nevertheless, cytotoxicity was observed for TA97 and TA102 with and without metabolization and for TA100 with metabolization. The measurement of beta-galactosidase induction in the SOS-chromotest was positive only for Escherichia coli PQ37 when metabolization enzymes were present. Using Balb/c 3T3 fibroblasts, DNA strand breaks induction by GSE was also investigated by the comet assay and no significative difference was detected for treated and no treated DNA for 60 min. Our data suggest that GSE although no mutagenic presents cytotoxic activity.