Inhibitory effect of nordihydroguaiaretic acid on the frequency of micronuclei induced by methyl methanesulfonate in vivo

Guidance for the use and interpretation of assays for monitoring anti-genotoxicity

Since DNA damage can occur spontaneously or be produced by the environmental genotoxins in living cells, it is important to investigate compounds that can reverse or protect DNA damage. An appropriate methodology is essential for the responsive identification of protection offered against DNA damage. This review includes information on the current state of knowledge on prokaryotic cell-based assays (SOS chromotest, umu test, vitotox assay) and cytogenetic techniques (micronucleus assay, chromosome aberration test and sister chromatid exchange assay) with an emphasis on the possibility to explore genoprotective compounds. Throughout the last decade, studies have extrapolated the scientific methodologies utilized for genotoxicity to assess genoprotective compounds. Therefore, shortcomings of genotoxicity studies are also mirrored in antigenotoxicity studies. While regulatory authorities around the world (OECD, US-EPA and ICH) continue to update diverse genotoxic assay strategies, there are still no clear guidelines/approaches for efficient experimental design to screen genoprotective compounds. As a consequence, non-synergetic and inconsistent implementation of the test method by the researchers to execute such simulations has been adopted, which inevitably results in unreliable findings. The review has made the first attempt to collect various facets of experimentally verified approaches for evaluating genoprotective compounds, as well as to acknowledge potential significance and constraints, and further focus on the assessment of end points which are required to validate such action. Henceforth, the review makes an incredible commitment by permitting readers to equate several components of their test arrangement with the provided simplified information, allowing the selection of convenient technique for the predefined compound from a central repository.

Classic Phytochemical Antioxidant and Lipoxygenase Inhibitor, Nordihydroguaiaretic Acid, Activates Phospholipase D through Oxidant Signaling and Tyrosine Phosphorylation Leading to Cytotoxicity in Lung Vascular Endothelial Cells

Nordihydroguaiaretic acid (NDGA), a dicatechol and phytochemical polyphenolic antioxidant and an established inhibitor of human arachidonic acid (AA) 5-lipoxygenase (LOX) and 15-LOX, is widely used to ascertain the role of LOXs in vascular endothelial cell (EC) function. As the modulatory effect of NDGA on phospholipase D (PLD), an important lipid signaling enzyme in ECs, thus far has not been reported, here we have investigated the modulation of PLD activity and its regulation by NDGA in the bovine pulmonary artery ECs (BPAECs). NDGA induced the activation of PLD (phosphatidic acid formation) in cells in a dose- and time-dependent fashion that was significantly attenuated by iron chelator and antioxidants. NDGA induced the formation of reactive oxygen species (ROS) in cells in a dose- and time-dependent manner as evidenced from fluorescence microscopy and fluorimetry of ROS and electron paramagnetic resonance spectroscopy of oxygen radicals. Also, NDGA caused a dose-dependent loss of intracellular glutathione (GSH) in BPAECs. Protein tyrosine kinase (PTyK)-specific inhibitors significantly attenuated NDGA-induced PLD activation in BPAECs. NDGA also induced a dose- and time-dependent phosphorylation of tyrosine in proteins in cells. NDGA caused in situ translocation and relocalization of both PLD₁ and PLD₂ isoforms, in a time-dependent fashion. Cyclooxygenase (COX) inhibitors were ineffective in attenuating NDGA-induced PLD activation in BPAECs, thus ruling out the activation of COXs by NDGA. NDGA inhibited the AA-LOX activity and leukotriene C₄ (LTC₄) formation in cells. On the other hand, the 5-LOX-specific inhibitors, 5, 8, 11, 14-eicosatetraynoic acid and kaempferol, were ineffective in activating PLD in BPAECs. Antioxidants and PTyK-specific inhibitors effectively attenuated NDGA cytotoxicity in BPAECs. The PLD-specific inhibitor, 5-fluoro-2-indolyl deschlorohalopemide (FIPI), significantly attenuated and protected against the NDGA-induced PLD activation and cytotoxicity in BPAECs. For the first time, these results demonstrated that NDGA, the classic phytochemical polyphenolic antioxidant and LOX inhibitor, activated PLD causing cytotoxicity in ECs through upstream oxidant signaling and protein tyrosine phosphorylation.

Transcriptome characterization of Larrea tridentata and identification of genes associated with phenylpropanoid metabolic pathways

Larrea tridentata (Sesse and Moc. ex DC.) Coville (family: Zygophyllaceae) is an aromatic evergreen shrub with resin-covered leaves, known to use in traditional medicine for diverse ailments. It also has immense pharmacological significance due to presence of powerful phenylpropanoids antioxidant, nordihydroguaiaretic acid (NDGA). The RNA sequence/transcriptome analyses connect the genomic information into the discovery of gene function. Hence, the acquaint analysis of L. tridentata is in lieu to characterize the transcriptome, and to identify the candidate genes involved in the phenylpropanoid biosynthetic pathway. To gain molecular insight, the bioinformatics analysis of transcriptome was performed. The total bases covered 48,630 contigs of length greater than 200 bp and above came out to 21,590,549 with an average GC content of 45% and an abundance of mononucleotide, SSR, including C3H, FAR1, and MADS transcription gene families. The best enzyme commission (EC) classification obtained from the assembled sequences represented major abundant enzyme classes e.g., RING-type E3 ubiquitin transferase and non-specific serine/threonine protein kinase. The KEGG pathway analysis mapped into 377 KEGG different metabolic pathways. The enrichment of phenylpropanoid biosynthesis pathways (22 genes i.e., phenylalanine ammonia-lyase, trans-cinnamate 4-monooxygenase, 4-coumarate-CoA ligase, cinnamoyl-CoA reductase, beta-glucosidase, shikimate O-hydroxycinnamoyl transferase, 5-O-(4-coumaroyl)-D-quinate 3'-monooxygenase, cinnamyl-alcohol dehydrogenase, peroxidase, coniferyl-alcohol glucosyltransferase, caffeoyl shikimate esterase, caffeoyl-CoA O-methyltransferase, caffeate O-methyltransferase, coniferyl-aldehyde dehydrogenase, feruloyl-CoA 6-hydroxylase, and ferulate-5-hydroxylase), and expression profile indicated antioxidant, anti-arthritic, and anticancer properties of L. tridentata. The present results could provide an important resource for squeezing biotechnological applications of L. tridentata.

Cytotoxic, pro-apoptotic, pro-oxidant, and non-genotoxic activities of a novel copper(II) complex against human cervical cancer

Cisplatin remains one of the most effective current chemotherapeutic agents; however, metal complexes synthesis has increased in order to produce new anti-neoplastic drugs with DNA binding and apoptotic activities in tumor cells and less toxicity for patients. In this study, we evaluated the cytotoxic activity of a novel copper(II) complex (LQM402) against cervical cancer cell lines and found that LQM402 exhibited selective cytotoxicity against HeLa and Ca Ski cells. FITC-annexin assay and DNA fragmentation indicated that apoptosis could be involved in HeLa cell death. Caspase 3/7 and cytochrome c analysis by immunoblotting suggest the intrinsic pathway. LQM402 is a lipid peroxidation inductor according to TBARS production. Additionally, the Ames and micronucleus tests demonstrated non-genotoxic activity for this compound in Salmonella typhimurium and CD1 mice, respectively. Therefore, LQM402 may be a promising and safe anti-cervical cancer compound.

Larrea tridentata (Creosote bush), an abundant plant of Mexican and US-American deserts and its metabolite nordihydroguaiaretic acid

Although controversial, Creosote bush, Larrea tridentata (Sesse and Moc. ex DC) Coville, is used to treat a variety of illnesses including infertility, rheumatism, arthritis, diabetes, gallbladder and kidney stones, pain and inflammation. Recently, it has been used as a nutritional supplement. The primary product extracted from this common plant of the arid regions of northern Mexico and Southwestern United States is the potent antioxidant nordihydroguaiaretic acid (NDGA). It was widely used during the 1950s as a food preservative and to preserve naturals fibers. Later it was banned after reports of toxicity during the early 1960s. Renal and hepatotoxicity are also reported for chronic use of creosote bush and NDGA. This article reviews traditional and contemporary uses and pharmacology, including toxicology of this plant widely used in Mexican traditional medicine.

Inhibitory effect of chlorophyllin on the frequency of micronuclei induced by sodium nitrite in mice

In this report the potency of chlorophyllin (CHL) was evaluated to prevent two types of damage produced by nitrite in mice: the increase of micronucleated polychromatic erythrocytes (MNPE) and the bone marrow toxicity, measured as the index of polychromatic erythrocytes/normochromatic erythrocytes (PE/NE). The study was done in eight groups of male mice. The first three groups were administered orally for 4 days with sodium nitrite (10, 15 and 20 mg/kg), the daily administration with nitrite was followed by an intraperitoneal administration of CHL (4 mg/kg), three more groups were administered with the same amounts of nitrite, a seventh group of mice was treated with distilled water while another was treated with CHL (4 mg/kg). Our study produced two main results: (a) no bone marrow injury was induced by any of the tested chemicals, as indicated with the PE/NE index, and (b) CHL protected (as high as 44%) the MNPE produced in nitrite treated mice.

Inhibitory effect of chamomile essential oil on the sister chromatid exchanges induced by daunorubicin and methyl methanesulfonate in mouse bone marrow

Different preparations of chamomile (Matricaria chamomilla) are used to treat various diseases, including inflammation and cancer; however, no studies on the plant's antigenotoxic capacity have been made. The aim of the present work was to determine the inhibitory effect of the chamomile essential oil (CO), on the sister chromatid exchanges (SCEs) produced by daunorubicin and methyl methanesulfonate (MMS) in mouse bone marrow cells. CO was analyzed and was found to contain 13 compounds, mainly bisabolol and its oxides, chamazulene, farnesene, germacrene and other sesquiterpenes. Initially, a toxic and a genotoxic analysis of CO were made; both showed negative results. To determine whether CO can inhibit the mutagenic effects induced by daunorubicin, one group of mice was administered corn oil, another group was treated with the mutagen (10 mg/kg), a third group was treated with 500 mg/kg of CO; three other groups were treated first with CO (5, 50 and 500 mg/kg) and then with 10 mg/kg of daunorubicin. In the case of MMS, the experimental groups consisted of the following: the negative control group which was administered corn oil, a group treated with 25 mg/kg of MMS, a group treated with 1000 mg/kg of CO, and three groups treated first with CO (250, 500 and 1000 mg/kg) and then with MMS (25 mg/kg). The results indicated a dose-dependent inhibitory effect on the SCEs formed by both mutagens. In the case of daunorubicin, a statistically significant result was observed in the three tested doses: from the lowest to the highest dose, the inhibitory values corresponded to 25.7, 63.1 and 75.5%. No alterations were found with respect to the cellular proliferation kinetics, but a reduction in the mitotic index was detected. As regards MMS, the inhibitory values were 24.8, 45.8 and 60.6%; no alterations were found in either the cellular proliferation kinetics or in the mitotic indices. Our results suggest that CO may be an effective antimutagen that could be considered for further study.

Inhibitory effect of naringin on the micronuclei induced by ifosfamide in mouse, and evaluation of its modulatory effect on the Cyp3a subfamily

Naringin (Nar) is a flavonone found in high amount in grapefruit. In in vitro studies to determine its antimutagenicity results have been both positive and negative. On the other hand, an increase in the bioavailability of some medicaments have been observed when these are ingested together with grapefruit. It has been suggested that the effect may be related to the inhibition of the human enzyme Cytochrome P450 (CYP) 3A4 by Nar, an enzyme with a high aminoacid sequence homology with the Cyp3a in mouse. The present study was designed for three main purposes: (1) to determine whether Nar has a genotoxic effect in mouse in vivo. This was evaluated by measuring the rate of micronucleated polychromatic erythrocytes (MNPE); (2) to determine its antigenotoxic and its anticytotoxic potential on the damage produced by ifosfamide (Ifos). The first study was done by scoring the rate of MNPE, and the second one by establishing the index polychromatic erythrocytes/normochromatic erythrocytes (PE/NE); and (3) to explore whether its antigenotoxic mechanism of action is related to an inhibitory effect of Nar on the expression of the Cyp3a enzyme, an effect which could avoid the biotransformation of Ifos. A single oral administration was used for all groups in the experiment: three groups were given different doses of Nar (50, 250, and 500 mg/kg), other groups received the same doses of Nar plus an administration of Ifos (60 mg/kg), another group treated with distilled water and another with Ifos (60 mg/kg) were used as negative and positive controls, respectively. The micronuclei and the cell scoring were made in blood samples taken from the tail of the animals at 0, 24, 48, 72, and 96 h. The results showed that Nar was neither genotoxic nor cytotoxic with the doses tested, but Ifos produced an increase in the rate of MNPE at 24 and 48 h. The highest value was 24+/-1.57 MNPE per thousand cells at 48 h. The index PE/NE was significantly reduced by Ifos at 24 and 48 h. Concerning the antigenotoxic capacity of Nar, a significant decrease was observed in the MNPE produced by Ifos at the three tested doses. This effect was dose-dependent, showing the highest reduction in MNPE frequency (54.2%) at 48 h with 500 mg/kg of Nar. However, no protection on the cytotoxicity produced by Ifos was observed. Immunoblot analysis was used to assess the Cyp3a expression in liver and intestinal microsomes from mouse exposed orally to Nar. An induction in the Cyp3a protein was observed in both intestinal and hepatic microsomes from treated mice. This induction correlated with an increase in erythromycin N-demethylase activity. These data suggest that other mechanism(s) are involved in the antigenotoxic action of naringin.