Search NEL Online

Journal Article 2014; 35(Suppl 2): 158-168 PubMed PMID: 25638381 Citation  Keywords:  Animals, Benzo(a)pyrene:administration & dosage, Carcinogens:administration & dosage, DNA Adducts:administration & dosage, Flavonols:administration & dosage, Male, Rats, Rats, Wistar,.   

<p>OBJECTIVES: Flavanol dihydromyricetin (DHM) has been shown to counteract acute ethanol (EtOH) intoxication and reduce excessive EtOH consumption. Since this flavonoid is being considered for human use, the in vivo study of DHM interactions with the cytochrome P450 (CYP) multienzyme system in the respect of metabolic activation of a model food-born carcinogen, benzo[a]pyrene (BaP), is of high importance. Flavonoids of known properties, alpha-naphthoflavone (ANF) and beta-naphthoflavone (BNF) were included into the study to compare their and DHM effects on BaP-DNA adduct formation. METH0 DS: The flavonoids were administered by oral gavage either 72 hrs prior or simultaneously with a single dose of BaP to experimental rats. The expression of CYP1A1/2 enzymes was examined based on the enzymatic activity with a marker substrate, 7-ethoxyresorufin, and on Western blots. The nuclease P1 version of the 32P-postlabeling assay was used to detect and quantify covalent DNA adducts formed by BaP.

RESULTS: Treatment of rats with a single dose of DHM or ANF prior to or simultaneously with BaP did not produce an increase in levels of CYP1A1 and in formation of BaP-DNA adducts in liver. BNF, a known inducer of CYP1A1, showed a synergistic effect on BaP-mediated CYP1A1 induction and BaP activation in liver. Contrary to that, in small intestine the stimulatory effect of BNF on both parameters was not detected. Animal pre-treatment with DHM or ANF before BaP administration resulted in a significant elevation of BaP-DNA adducts, namely in the distal part of small intestine, while the CYP1A1 mediated 7-ethoxyresorufin-O-deethylation (EROD) was decreased markedly. It is important to note that under all regimens of animal treatment, DHM or ANF produced the higher inhibitory effect on the BaP-DNA adduct formation and BaP-induced EROD activity of CYP1A1 when administered simultaneously than sequentially with BaP. Our data show that DHM or ANF did not enhance the BaP-activation leading to BaP-mediated genotoxicity (the formation of BaP-DNA adducts) in rat liver, however, in small intestine the pretreatment of rats with these flavonoids may enhance BaP genotoxicity.

CONCLUSIONS: The data indicate that the intake of DHM prior to or simultaneously with the administration of BaP may increase the risk of a BaP-induced tumorigenesis in small intestine.p>...

Read abstract  Full text PDF

Journal Article 2014; 35(Suppl 2): 155-157 PubMed PMID: 25638380 Citation  Keywords:  Adjuvants, Immunologic:pharmacology, Animals, Cytokines:metabolism, Female, Hemocyanin:pharmacology, Mice, Mice, Inbred BALB C, Models, Animal, Oximes:pharmacology, Pyridinium Compounds:pharmacology,.   

<p>OBJECTIVES: HI-6 or asoxime in some sources is an antidotum for nerve agents. In recent experiments, implication of HI-6 in immunity response was proved; however, the issue was not studied in details. In this experiment, role of cytokines in HI-6 impact on immunity was searched. DESIG N: BALB/c mice were exposed to saline, HI-6 in a dose 1-100 mg/kg and/or 1 keyhole limpet hemocyanin (KLH) 1 mg/kg. Mice were sacrificed 21 days after experiment beginning and interleukins (IL) 1, 2, 4, 6 were determined by Enzyme Linked Immunosorbent Assay (ELISA).

RESULTS: The animals had no pathological manifestation. From the tested cytokines, no significant alteration was found for the IL-1, IL-4 and IL-6. IL-2 was significantly increased in a dose response manner.

CONCLUSIONS: The experimental data well correlates with the previous work where HI-6 caused increase of antibodies production. HI-6 is suitable to be used as an adjuvant whenever immunity should be pharmacologically altered.p>...

Read abstract  Full text PDF

Journal Article 2014; 35(Suppl 2): 149-154 PubMed PMID: 25638379 Citation  Keywords:  Antioxidants:pharmacology, DNA Damage:drug effects, Emodin:pharmacology, Humans, Mutagenicity Tests, Mutagens:pharmacology, Mutation:drug effects,.   

<p>OBJECTIVES: Emodin is a bioactive anthraquinone that has diverse biological effects. It is also known as a biosynthetic precursor of hypericin. The purpose of this study was to assess mechanisms of potential genotoxic and antioxidant effects of emodin. We also investigated the potential genotoxic effect of photoactivated emodin.

METHODS: Potential genotoxicity was determined by the alkaline comet assay and the Ames test. The potential DNA protectivity of emodin was determined by the DNA-topology assay. On purpose to clarify molecular mechanism of its DNA protectivity against Fe(2+)-induced DNA breaks, three different assays were used (Reducing power-, DPPH- and Fe(2+)-chelating assay).

RESULTS: Using the alkaline comet assay and the Ames test we confirmed the genotoxic effect of both non-photoactivated and photoactivated emodin in a dose-dependent manner. Genotoxicity of photoactivated emodin did not differ from that obtained with non-photoactivated one. The DNA-topology assay revealed a DNA-protective activity of emodin. In the reducing power and DPPH assays emodin exhibited weak antioxidant activities. We did not observe any chelating activity of emodin in the Fe(2+)-chelating assay.

CONCLUSIONS: We found out that emodin exhibited dual activities. On one side it was genotoxic inducing primary DNA lessions (determined by the comet assay) as well as gene mutations (determined by the Ames test). On the other side it exhibited DNA-protective activity (determined by the DNA-topology assay). Molecular mechanism underlying this DNA protective effect can be attributed to its free radicals scavenging and reducing activities.p>...

Read abstract  Full text PDF

Journal Article 2014; 35(Suppl 2): 141-148 PubMed PMID: 25638378 Citation  Keywords:  Animals, Electron Transport Complex II:drug effects, Formazans:metabolism, Interferon-gamma:pharmacology, Mice, Mice, Inbred C57BL, Peritoneum:cytology, Pyrimidines:pharmacology, Spleen:cytology,.   

<p>OBJECTIVES: Formation of formazan is a commonly used measure of cytotoxicity of compounds. It is a product of reduction of tetrazolium salts such as 4-[3- (4-iodophenyl)-2- (4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST-1) and 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyltetrazolium chloride. The extent of substrates reduction reflects the activity of enzymes succinate dehydrogenase (SDH; respiratory complex II) and lactate dehydrogenase (LDH), respectively. The aim of present study was a) to investigate formazan formation under the conditions of in vitro stimulation of cells with interferon-γ (IFN-γ) and lipopolysaccharide (LPS), and b) to analyse possible interference of pyrimidine analogues with formazan production.

METHODS: Peritoneal cells and splenocytes were obtained from C57BL/6 mice. They were cultured at 37 degrees C, 5% CO2 in humidified incubator. Levels of formazan were determined at the interval of 24 h of culture using the WST-1 and LDH assays. Nitric oxide (NO) was activated by IFN-γ plus LPS and assayed by Griess reagent 24 h afterwards. Pyrimidines were applied concomitantly with immunostimulatory agents.

RESULTS: IFN-γ enhanced concentration of SDH-produced formazan by macrophages (not by splenocytes) by approximately 50%. The activity of LDH remained unaffected. LPS was ineffective in both cases. While pyrimidines with NO-inhibitory properties suppressed the IFN-γ-enhanced levels of SDH-produced formazan, they did not change the LDH-dependent formazan production.

CONCLUSION: IFN-γ augments the SDH-produced formazan by macrophages. It does not change the LDH-dependent formazan formation. The enhancing effect may have a significant impact upon the appropriate interpretation of cytotoxic properties of drugs investigated under the conditions of immune stimulation of cells.p>...

Read abstract  Full text PDF

Journal Article 2014; 35(Suppl 2): 123-132 PubMed PMID: 25638376 Citation  Keywords:  Animals, Aristolochic Acids:metabolism, Dicumarol:pharmacology, Enzyme Inhibitors:pharmacology, Humans, Quinone Reductases:metabolism, Rats,.   

<p>OBJECTIVES: Dicoumarol is known to act as an inhibitor of

NAD(P)H: quinone oxidoreductase (NQO1). This cytosolic reductase significantly contributes to the genotoxicity of the nephrotoxic and carcinogenic alkaloid aristolochic acid I (AAI). Aristolochic acid causes aristolochic acid nephropathy (AAN), and Balkan endemic nephropathy (BEN), as well as associated urothelial malignancies. NQO1 is the most efficient enzyme responsible for the reductive bioactivation of AAI to species forming covalent AAI-DNA adducts. However, it is still not known how dicoumarol influences the NQO1-mediated reductive bioactivation of AAI.

METHODS: AAI-DNA adduct formation was determined by 32P-postlabeling. Expression of NQO1 mRNA and NQO1 protein was determined by real-time polymerase chain reaction and Western blotting, respectively.

RESULTS: In this study, dicoumarol inhibited AAI bioactivation to form AAI-DNA adducts mediated by rat and human NQO1 in vitro as expected. We however, demonstrated that dicoumarol acts as an inducer of NQO1 in kidney and lung of rats treated with this NQO1 inhibitor in vivo, both at protein and activity levels. This NQO1 induction increased the potency of kidney cytosol to bioactivate AAI and elevated AAI-DNA adduct levels were found in ex-vivo incubations of AAI with renal cytosols and DNA. NQO1 mRNA levels were induced in liver only by dicoumarol.

CONCLUSION: Our results indicate a dual role of dicoumarol in NQO1-mediated genotoxicty of AAI. It acts both as an NQO1 inhibitor mainly in vitro and as an NQO1 inducer if administered to rats.p>...

Read abstract  Full text PDF

Journal Article 2014; 35(Suppl 2): 114-122 PubMed PMID: 25638375 Citation  Keywords:  Animals, Aryl Hydrocarbon Hydroxylases:metabolism, Cell Membrane:metabolism, Cytochrome P450 Family 2, Cytochromes b5:metabolism,.   

<p>OBJECTIVES: The mammalian mixed function oxidase (MFO) system participates in hydroxylation of many hydrophobic endogenous compounds as well as xenobiotics such as drugs and carcinogens. This biotransformation system, located in a membrane of endoplasmic reticulum, consists of cytochrome P-450 (P450), NADPH:P450 oxidoreductase and a facultative component, cytochrome b5. The knowledge of the interactions among the individual components of the MFO system is essential to understand the relationships between the structure and function of this system that finally dictate a qualitative and quantitative pattern of produced metabolites (e.g. detoxified xenobiotics and/or activated carcinogens). To elucidate the quantitative aspects of the interactions within the MFO system we acquired the photo-initiated cross-linking approach.

METHODS: The photo-initiated cross-linking employing cytochrome b5 as a protein nanoprobe [an amino acid analogue of methionine (pMet) was incorporated into cytochrome b5 sequence during recombinant expression] was used to quantify its interaction with P450 2B4 in a functional membrane complex. The cross-linking was initiated by UV-irradiation that formed from a pMet photolabile diazirine group highly reactive carbene biradical. This biradical is able to covalently bind amino acids in the close proximity and to form cross-link. The Met 96 of cytochrome b5 is situated in a linker region between its catalytic and membrane domains, while Met 126 and 131 are located in its membrane domain. The combination of several methods (electrophoresis in polyacrylamide gel, isoelectric focusing, Edman N-terminal degradation and amino acid analysis) was employed to characterize the molar ratio of P450 2B4 to cytochrome b5 in formed covalent cross-links to quantify their transient interactions.

RESULTS: The successfully produced cytochrome b5 nanoprobe (with confirmed pMet incorporation by mass spectrometry) stimulates the catalytical activity of P450 2B4 when reconstituted with NADPH:P450 oxidoreductase in vitro in dilauroylphosphatidylcholine (DLPC) vesicles. The cross-linking was carried out in similar reconstituted system without NADPH:P450 oxidoreductase, and at least three products were separated on 1D SDS-PAGE. The molar ratio of P450 to cytochrome b5 in each complex was estimated using the above-mentioned combination of methods as 1:1, 1:2 and 2:1.

CONCLUSIONS: The results demonstrate the utility of cytochrome b5 nanoprobe to study the interactions in MFO system. Using this nanoprobe, heterodimer with P450 2B4 and in addition also heterooligomers were identified, suggesting rather complex interactions of both proteins in this system that suppose the formation of such multimeric structures in the membrane of endoplasmic reticulum.p>...

Read abstract  Full text PDF

Journal Article 2014; 35(Suppl 2): 105-113 PubMed PMID: 25638374 Citation  Keywords:  Benzo(a)pyrene:metabolism, Cytochrome P-450 CYP1A1:metabolism, Cytochromes b5:metabolism, Humans, NADH, NADPH Oxidoreductases:metabolism,.   

<p>OBJECTIVES: Cytochrome P450 (CYP) 1A1 located in the membrane of endoplasmic reticulum is the most important enzyme in both activation and detoxification of carcinogenic benzo[a]pyrene (BaP), in combination with microsomal epoxide hydrolase (mEH). However, it is still not clearly explained how the electron transfer is mediated by NADPH:CYP oxidoreductase (POR), another component of the microsomal enzymatic system, on CYP1A1 during BaP oxidation, and whether microsomal cytochrome b5 might influence this electron transfer.

METHODS: High performance liquid chromatography (HPLC) was employed for separation of BaP metabolites formed by enzymatic systems containing human CYP1A1.

RESULTS: Human CYP1A1 expressed with POR in eukaryotic and prokaryotic expression cellular systems, in microsomes of insect cells (Supersomes) and in a membrane fraction of Escherichia coli, respectively, and these enzyme systems reconstituted with purified cytochrome b5 were utilized to study BaP oxidation. Human CYP1A1 expressed in Supersomes oxidized BaP to seven metabolites [7,8- and 9,10-dihydrodiols, 1,6-dione, 3,6-dione, 3- and 9-phenols, and a metabolite with unknown structure (Mx)], whereas this enzyme expressed in membranes of E. coli formed only the metabolites 1,6- and 3,6-diones, 3- and 9-phenols, and Mx. Addition of cytochrome b5 to CYP1A1 expressed in the eukaryotic system led to a more than 2-fold increase in BaP metabolism, but had essentially no effect on BaP oxidation by CYP1A1 expressed in E. coli.

CONCLUSION: The effect of cytochrome b5 on CYP1A1 conformation and the electron transfer to this enzyme may contribute to the cytochrome b5-mediated stimulation of BaP oxidation.p>...

Read abstract  Full text PDF

Journal Article 2014; 35(Suppl 2): 99-104 PubMed PMID: 25638373 Citation  Keywords:  Animals, Antibodies:immunology, Bacterial Infections:prevention & control, Cell Line, Chickens, Egg Yolk:immunology, Epithelial Cells:immunology, Humans, Immunoglobulin Fab Fragments:immunology, Immunoglobulins:immunology, Inflammation:immunology, Lung:im.   

<p>OBJECTIVES: As an alternative therapeutic approach for the prevention and treatment of bacterial infections with P. aeruginosa of cystic fibrosis (CF) patients, chicken yolk antibodies (IgY) could be used. The most significant advantage of IgY, in contrast to mammalian IgG, consists in the fact, that when bound to the antigen, they usually do not induce inflammatory reaction. In addition, the simplicity of egg production and the ease of IgY preparation makes this kind of antibody an excellent tool for passive immunization. Thus, the aim of our project was to study the effect of IgY and its Fab fragment on the potential induction of pro-inflammatory reactions in lung epithelial cells.

METHODS: Chicken IgY were prepared from pooled egg yolks. Fab fragmens of IgY were purified from the papain digest of IgY using DEAE-Sephacel ion exchange chromatography. Their purity was verified by SDS electrophoresis in polyacrylamide gel. Immortalized human cell lines, CuFi (CF patient) and NuLi (healthy subject), and A549 (human adenocarcinoma cells) were exposed to IgY, Fab, OVA, LPS (positive control), PBS (negative control), and human and goat IgG for 24 hours. The concentration of pro-inflammatory cytokines TNF-α, IL-1β, IL-6 and GM-CSF were determined in cell media using the BioPlex method, which enables the quantification of multiple analytes simultaneously in one sample.

RESULTS: Our results show that i) the Fab fragment induced levels of some proinflammatory cytokines, when compared to the PBS control, whereas ii) chicken IgYs did not induce any notable production of pro-inflammatory cytokines in contrast to intense effect of LPS on TNF-α and GM-CSF. In summary, our data show that levels of all cytokines are comparable with physiological values in human serum except of IL-1β, which concentration in cell medium was markedly elevated by Fab fragment.

CONCLUSIONS: The present data indicate that IgY are not inflammatory for lung cells and thus they are possibly applicable for prevention of airway bacterial infections.p>...

Read abstract  Full text PDF